Use JRuby 1.7.22 on Travis

With `rvm: jruby` JRuby 1.7.19 is used and the version has an issue with
Bundler upgrade.

jruby/jruby#1595

Author: yujinakayama

.travis.yml

@@ -23,13 +23,13 @@ rvm:
   - rbx
 matrix:
   include:
-    - rvm: jruby
+    - rvm: jruby-1.7.22
       env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false -Xcompat.version=2.0'
     - rvm: jruby-head
       env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false'
-    - rvm: jruby-18mode
-      env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false'
-    - rvm: jruby
+    - rvm: jruby-1.7.22
+      env: JRUBY_OPTS='--1.8 --server -Xcompile.invokedynamic=false'
+    - rvm: jruby-1.7.22
       env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false'
   allow_failures:
     - rvm: jruby-head