Fix typo in safeContextKeyword message
Extract own settings into google preset

Fixes #268
Fixes #197
Added disallowTrailingComma: disallowing the extra comma following the final element of an array or object literal.
Updated package description so as not to troll pedants
Added require-trailing-comma as well as improving test coverage for disallow-trailing-comma.
Added disallowSpaceBeforeBlockStatements and requireSpaceBeforeBlockStatements.