Add appraisal gem
Add gemfiles for 4.0 and 4.1
Add appraisal gemfiles to build matrix
Add MRI 2.1.2 while we're at it
Remove gemfile artifact
[ci skip]
Merge pull request #17 from Absolventa/add_appraisals

+1 for that. Let's roll with it. 

Add appraisals w/ gemfiles for Rails v4.0 + v4.1