Removed assert: true when installing dpl gem
Make JVM builds aware of gradle wrapper

JVM alreads know about build.gradle to make builds using pre-installed
gradle binaries. But Gradleware recomends a feature[1] where a gradle
wrapper script can be used so build can be more smart about required
gradle versions.

This commit makes Travis smart about Gradle smartness.

[1]: http://www.gradle.org/docs/current/userguide/gradle_wrapper.html
Without sbt configuration, scala behaves like jvm

Avoid code repetitions between scala builder and other JVM languages, by
applying same rules for build tool detection (Gradle, Maven and Ant)
Maintain the same code style for checking file existence
small refactor for bundle command
fix clause nesting
Merge branch 'master' into rkh-casher
set up directory cache
Added support for deploying to multiple providers
move configuration into cache section, like apt
always cache bundler when it has been explicitely enabled, only cache if there is a Gemfile.lock if it has been implicitely enabled
improve bundler path logic
fix regexp
implement uri signing
fix for ruby 1.9
Merge pull request #130 from gildegoma/dry-scala-and-jvm

Without sbt configuration, scala builder should behave like other jvm languages
Merge pull request #126 from andrewhr/ar-gradle-wrapper-for-jvm

Make JVM builds aware of gradle wrapper
Change DNS resolv entries to the Ashburn servers.
One less \
Hide output for change of DNS servers.