Cleaned up Rake and Testing files

Dropped support for Rails 3
Dropped support for Ruby 1.8
Added support for Rails 4
Constrained paperclip to 3.3..4 for now
Merge pull request #77 from ScotterC/clean-up-appraisal

Cleaned up Rake and Testing files
Testing Support for paperclip 4

Validation now required
Merge pull request #78 from ScotterC/paperclip-4

Testing Support for paperclip 4