Drop support for Rubinius

The parallelized hook runs fail for Rubinius builds. I don't have enough
knowledge of this Ruby runtime to be able to diagnose it (nor the time,
frankly).

We should not include it in our list of supported Rubies if it is not
passing tests.

Author: sds

.travis.yml

@@ -11,11 +11,6 @@ rvm:
   - 2.2
   - 2.3.0
   - jruby-19mode
-  - rbx-2
-
-matrix:
-  allow_failures:
-    - rvm: rbx-2
 
 before_script:
   - git config --global user.email "travis@travis.ci"

CHANGELOG.md

@@ -6,6 +6,10 @@
   `GIT_AUTHOR_NAME`/`GIT_AUTHOR_EMAIL` environment variables, respectively
 * Fix `JavaCheckstyle` pre-commit hook to ignore `[ERROR]` prefix when parsing
   output messages
+* Official support for Rubinius has been dropped. It will probably still work
+  for most use cases, but parallelized hook runs may be problematic. If someone
+  from the community is willing to step up to support it, we'll gladly add it
+  back.
 
 ## 0.32.0
 

README.md

@@ -57,7 +57,6 @@ This project aims to support the following Ruby runtimes:
 
 * MRI 1.9.3 & 2.x
 * JRuby 1.7.x
-* Rubinius 2.x
 
 Windows is currently supported only for MRI Ruby 2.x