ARROW-209: [C++] Triage builds due to unavailable LLVM apt repo

For now, this unblocks builds until we can resolve the LLVM apt issue.

Author: Wes McKinney <wesm@apache.org>

Closes #84 from wesm/ARROW-209 and squashes the following commits:

c6bf166 [Wes McKinney] Remove clang-* packages from apt list
30d8c5c [Wes McKinney] Temporarily disable clang-format and clang-tidy checks in Travis CI build

Author: wesm

.travis.yml

@@ -5,10 +5,7 @@ addons:
     sources:
     - ubuntu-toolchain-r-test
     - kalakris-cmake
-    - llvm-toolchain-precise-3.7
     packages:
-    - clang-format-3.7
-    - clang-tidy-3.7
     - gcc-4.9   # Needed for C++11
     - g++-4.9   # Needed for C++11
     - gdb

ci/travis_script_cpp.sh

@@ -7,10 +7,14 @@ set -e
 pushd $CPP_BUILD_DIR
 
 make lint
-if [ $TRAVIS_OS_NAME == "linux" ]; then
-  make check-format
-  make check-clang-tidy
-fi
+
+# ARROW-209: checks depending on the LLVM toolchain are disabled temporarily
+# until we are able to install the full LLVM toolchain in Travis CI again
+
+# if [ $TRAVIS_OS_NAME == "linux" ]; then
+#   make check-format
+#   make check-clang-tidy
+# fi
 
 ctest -L unittest