build should fail when there are missing headers and ignoreFailures=false (#13)

StopActionException only causes that action to stop, and continues the build with the next action.
I've changed it to instead throw GradleException, following the lead of the Test task.

http://www.gradle.org/docs/current/javadoc/org/gradle/api/tasks/StopActionException.html
Merge pull request #15 from davidmc24/issue-13

fix "ignoreFailures=false does not fail build" (issue #13)
Create base task for other tasks to hang off of
Set a better default for grails code.
Merge pull request #18 from quidryan/base-tasks

Create base task for other tasks to hang off of
Merge pull request #19 from quidryan/additional-mappings

Set a better default for grails code.
Move version to properties file, to make releases easier (either via Artifactory plugin or gradle-release plugin)
Properly use method to query skipExistingHeader so that conventions are used. Use skipExistingHeaders in check tasks.
Fixing exception, it was changed to work around ignoreFailure not being pull from the convention.
Forcing name, for automated builds
Switch back to a real RuntimeException
Merge pull request #17 from quidryan/skipHeaders

Skip headers fix for #16
Moved License task to package
Added default task
Revert "Moved License task to package"

This reverts commit aba57da0e21e7cba2220dce1a92de56b196540bd.
Cleanup
gitignore
Upgraded to Guava 14.0.1 (fixes #21)
Fixes #22 Use create instead of add as the deprecation warning suggests
Fixed #12 by reporting on license dependencies