[CI] Replaced gemfile specification for Travis with custom TEST_BUNDLE_GEMFILE environment variable

Run tests like this locally:

    $ SERVER=start TEST_BUNDLE_GEMFILE=$PWD/elasticsearch-model/gemfiles/3.0.gemfile TEST_CLUSTER_COMMAND=/tmp/elasticsearch-1.0.0.RC1/bin/elasticsearch bundle exec rake test:all

    $ SERVER=start TEST_BUNDLE_GEMFILE=$PWD/elasticsearch-model/gemfiles/4.0.gemfile TEST_CLUSTER_COMMAND=/tmp/elasticsearch-1.0.0.RC1/bin/elasticsearch bundle exec rake test:all

Author: karmi

.travis.yml

@@ -16,19 +16,20 @@ rvm:
 jdk:
   - openjdk7
 
+env:
+  - TEST_BUNDLE_GEMFILE=$PWD/elasticsearch/elasticsearch-rails/elasticsearch-model/gemfiles/3.0.gemfile
+  - TEST_BUNDLE_GEMFILE=$PWD/elasticsearch/elasticsearch-rails/elasticsearch-model/gemfiles/4.0.gemfile
+
 services:
   - mongodb
 
 before_script:
+  - ls -la /usr/share/elasticsearch/bin/elasticsearch
   - rake bundle:clean
   - rake bundle:install
 
 script:
-  - SERVER=start bundle exec rake test:all
-
-gemfile:
-  - $PWD/elasticsearch-model/gemfiles/3.0.gemfile
-  - $PWD/elasticsearch-model/gemfiles/4.0.gemfile
+  - SERVER=start TEST_CLUSTER_COMMAND=/usr/share/elasticsearch/bin/elasticsearch TEST_BUNDLE_GEMFILE=$TEST_BUNDLE_GEMFILE bundle exec rake test:all
 
 notifications:
   disable: true