Merge pull request #95 from futuresystems/milestone/v0.3.1

prep for PEARC17 and Ubuntu 16.04 support

Merge branch 'unstable'

* unstable:
  add upgrading requirements to upgrade procedure
  update changelog
  have .cluster.py assign zookeeper_id in host_vars
  upgrades vcl v0.2.2 -> v0.2.3

Merge branch 'unstable'

* unstable:
  update changelog
  bump vcl to v0.2.2
  use a default cache valid time of 24 hours
  update submodule: hbase (fixes url breakage)

Merge branch 'unstable'

* unstable:
  add v0.2.2 changes to changelog
  update changelog for v0.2.1
  describe upgrade procedure in readme
  upgrades vcl v0.2.0 -> v0.2.1 (see issue vcl/#3)

fix commit for spark role submodule

Merge branch 'unstable'

* unstable: (21 commits)
  add changelog
  update readme with vcl ssh information
  fix permissions for uploading data to hdfs
  use m1.small flavor by default
  Revert "add hack to update inventory with floating ips"
  upgrade vcl to v0.2.0
  switch to binary version of spark
  examples/nist: indicate data import may take time
  examples/nist: fix extraction permission errors
  examples/nist: fix error on data import to hdfs
  fix monitoring: missing -X for ssh command
  tell user how to access ganglia interface
  add analytics and hbase to all addons playbook
  emphasize need for --recursive when cloning
  typo fix
  tell user to add ssh key to github.com
  add hack to update inventory with floating ips
  start zookeeper before formatting namenode
  update readme on frontend access
  update readme on zookeeper_id generation
  ...

Merge branch 'unstable'

* unstable:
  use frozen requirements by default
  use ssh_users variable in hadoop play (closes #55)