[#80157228] Fix where.not

Bump version to 0.5.2
Update for Rails 4

Add dependencies to gemspec to ensure we are notified of necessary updates
Remove Rails 3 compatibility (attr_accessible)
Bump version to 0.6.0
Remove pry dependency
Remove ruby version dependency
Merge pull request #2 from hired/rails4

removes Rails 3.2 compatibility and an update for Rails 4