Lowered requirement to Grails 2.0 minimum.

Grails 2.0 should be using Groovy 1.8, which is the dependency for the
Json package.

Incompatible with previous versions, or those previous versions which do
not have Groovy 1.8.
Merge branch 'development' of github.com:aaron-brown/grails-smartionary into development

Conflicts:
	SmartionaryGrailsPlugin.groovy
Updating version.

Release was specified as 1.0, but I'm adding 1.0.0 for consistency.