Added warts for List head, tail and last.
updated README with List warts.
spacing.
Merge pull request #114 from jonoabroad/master

Adding warts for List operations head,tail and last
Create sbt-wartremover sbt plugin
Move src/ to core/src/ and sbt-wartremover/ to sbt-plugin/
Add trigger and autoImport to sbt-plugin
Fix the `wartremover` shell script
Update README with regard to the new sbt plugin