Added a list of authors and contributors.

The authors were generated with the `git` command provided in the file and
cleaned up. Some of the names/emails were clearly bogus (one email was
attributed to several names, so their emails are now marked as `<?>`); some
names were placeholders or emails were using `@users.noreply.github.com`, etc.

The author (aka copyright holder) list is assumed to be DataStax due to the CLA
which included copyright assignment. It's possible that there are other
copyright holders who contributed to Titan prior to DataStax's acquisition of
Aurelius, but that would need to be verified separately.

Signed-off-by: Misha Brukman <mbrukman@google.com>

AUTHORS.txt

@@ -0,0 +1,16 @@
+# This is the official list of JanusGraph authors for copyright purposes.
+# This file is distinct from the CONTRIBUTORS.txt files.
+# See the latter for an explanation.
+
+# Names should be added to this file as one of
+#     Organization's name
+#     Organization's name <email pattern1> ...
+#     Individual's name <email1>
+#     Individual's name <email1> <email2> <emailN>
+# See CONTRIBUTORS.txt for the meaning of multiple email addresses.
+
+# Please keep the list sorted.
+
+DataStax
+Dylan Bethune-Waddell <dylan.bethune.waddell@mail.utoronto.ca>
+Google

CONTRIBUTORS.txt

@@ -0,0 +1,90 @@
+# This is the official list of people who have contributed to JanusGraph,
+# including contributors to Titan.
+#
+# The AUTHORS.txt file lists the copyright holders; this file lists people. For
+# example, employees of an organization who assign copyright to their
+# organization are listed here but not in AUTHORS.txt, because their
+# organization holds the copyright. Similarly, contributors who assigned
+# copyright to a party other than their employer (such as Titan contributors who
+# assigned copyright to DataStax) will appear in this list, but not in
+# AUTHORS.txt file.
+#
+# Note: it's unclear at this time whether contributors to Titan pre-acquisition
+# of Aurelius by DataStax own their contributions, or whether they signed away
+# their copyright as well. This needs further investigation.
+#
+# When adding J Random Contributor's name to this file, either J's name or J's
+# organization's name should be added to the AUTHORS.txt file, depending on
+# whether the individual or corporate CLA was used.
+
+# The original list was generated via:
+#
+#     $ git log --all --format='%aN <%cE>' | sort -u --ignore-case
+#
+# and manual cleanup.
+
+# Names should be added to this file like so:
+#     Individual's name <email1>
+#     Individual's name <email1> <email2> <emailN>
+
+# Please keep the list sorted.
+
+Achintha Gunasekara <achintha@me.com>
+Alexander Patrikalakis <amcp@mit.edu>
+Alexander Vieth <alex@lagoa.com>
+Anderson de Andrade <adeandrade@verticalscope.com>
+Andy Keffalas <akeffala@nearinfinity.com>
+Austin Harris <austin.w.harris@gmail.com>
+Blake Eggleston <bdeggleston@gmail.com>
+Bobby Norton <bobby@thinkaurelius.com>
+Brad Anderson <brad@sankatygroup.com>
+Brennon York <?>
+Bryn Cooke <BrynCooke@gmail.com>
+Christian Bellina <christian.bellina@ef.com>
+Collin Scangarella <spmva@genoprime.com>
+Cris Weber <cris.weber@gmail.com>
+Dan LaRocque <dalaro@hopcount.org>
+Daniel Kuppitz <daniel_kuppitz@hotmail.com>
+Danny Thomas <dmthomas@gmail.com>
+Dave Brosius <dbrosius@mebigfatguy.com>
+David Robinson <drobin1437@gmail.com>
+deiflaender <?>
+Dylan Bethune-Waddell <dylan.bethune.waddell@mail.utoronto.ca>
+Eric Lubow <eric@lubow.org>
+Erick Tryzelaar <erickt@lab41.org>
+Fabrice Bellingard <?>
+Frederick Haebin Na <haebin.na@gmail.com>
+Homer Strong <homer.strong@gmail.com>
+janar <janar@yahoo-inc.com>
+Jason Plurad <pluradj@us.ibm.com>
+Joe Ferner <joe@fernsroth.com>
+Joshua Shinavier <josh@fortytwo.net>
+Justin Corpron <justin.corpron@justinc-677.glassdoor.local>
+Karthik Ramachandran <kramachandran@iqt.com>
+ksenji <ksenji@ebay.com>
+Leifur Halldor Asgeirsson <leifurhauks@gmail.com>
+Mark McCraw <mark.mccraw@sas.com>
+Marko A. Rodriguez <okrammarko@gmail.com>
+Matt Pouttu-Clarke <voidpointer101@gmail.com>
+Matthias Broecheler <me@matthiasb.com>
+Michael Klishin <michael@defprotocol.org>
+Mike Dias <?>
+Mike McMahon <mmcm@comcast.net>
+Misha Brukman <mbrukman@google.com>
+MrKeyholder <fractalf@gmail.com>
+Nik Everett <neverett@wikimedia.org>
+Pavel Yaskevich <pyaskevich@twitter.com> <xedin@apache.org>
+Peter Beaman <pbeaman@akiban.com>
+Petter Aas <aaspet@gmail.com> <petter.aas@fronter.com>
+Pieter <pieter@pieter-HP-EliteBook-8570w.(none)>
+PommeVerte <dylan.millikin@gmail.com>
+Ranger Tsao <cao.zhifu@gmail.com>
+Richard Doll <rdoll@care-view.com>
+Solon Gordon <solon@knewton.com>
+Stephen Mallette <spmallette@gmail.com> <spmva@genoprime.com>
+Ted Crossman <tedo@rockmelt.com>
+Ted Wilmes <twilmes@gmail.com>
+Tim Wu <tim@urx.com>
+tsecheran <tsecheran@yahoo.com>
+Wytse Visser <wytsevisser@gmail.com>
+Yuhao Bi <byh0831@gmail.com>