fix #13: incompatibility with Gradle 1.8

* Creating a separate branch 'gradle-1.8' for gradle 1.8 compatibility.
* Upgraded the gradle wrapper and related files to gradle 1.8.
* Changed the 'groovy' configuration reference to 'compile' as per
  deprecation instructions from gradle (the groovy configuration
  will be removed in gradle 2.0 and is deprecated now)
* Upgraded the plugin version to 1.2.2
Merge pull request #14 from mbjarland/gradle-1.8

fix #13: incompatibility with Gradle 1.8
Bump version to 1.8.0 to mirror Gradle compatibility
support subfolders for lesscss task

if the source files are organized in subfolders, the same folder
hierarchy will be recreated in the destination
Update docs to use  task instead of . Fixes #15
Merge LESS subfolder support from @conceptboard.
fixes #18 (less compiler doesn't report the file an error occurred in)

Also upgrading the plugin artifact version to 1.8.1 to enable clients
to download this fixed version. Also added an extra task for creating
a fat jar with all transitive dependencies. Useful when doing local
testing of the plugin code.