Update codequality/checkstyle.xml

Removing as it appears to no longer be available in the latest version of checkstyle that comes with gradle 1.4
Upgrading to Gradle 1.4
Switching to bintray for dependencies (same as Maven Central)
Move gradle-release dependency to bintray
Use newer version of license-gradle-plugin that fixes skipExistingHeaders field
Add sonatype snapshot repository
Using latest features of release plugin
Upgrading release process
Matching wrapper to 1.5
Automatically aggregate and publish docs (java,groovy,scala)
Make uploadMavenCentral task, that encompasses other tasks
Handle unavailable sonatype properties
Verify before we can't take it back, use preferredVersion variable
Passing status to Artifactory builds
Fixing aggregateJavadoc
Adding mavenLocal() for local resolution
making Func0 covariant in its return type, cleaning up a few warnings, removing a bit of unused code
added variance to Func1 (hopefully) everywhere...
added variance to Func2, too
added variance to all other Func*; this breaks Scala for good, it seems, as long as Observable remains invariant