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.
fixes #18: further formatting of less compilation error messages
fixes #18: removing invalid test change to artifact version
Upgrading readme to the correct release version 1.8.1 as per build.gradle
Merge pull request #19 from mbjarland/master

fixes #18 (less compiler doesn't report the file an error occurred in)