include call to get groovy-contributions as requested in pull request #525 by jnorthr
Revert "include call to get groovy-contributions as requested in pull request #525 by jnorthr"

This reverts commit e39083dc69bbf1ee0c08655323244f017d3ea388.

The groovy-contributions guide will not be part of the language specification, but it will be published on the groovy website.
grammatical/formatting change and mentioned GMavenPlus support for grooid
Merge pull request #530 from keeganwitt/master

grammatical/formatting changes, added GMavenPlus grooid comment
GROOVY-6956: Align @DelegatesTo with @ClosureParams with regards to generics type handling
Documentation for GROOVY-6956