Add option for allowing blank values
Merge pull request #12 from johannesjasper/master

Add option for allowing blank values
Move Bundler.require to get coverage back.
Release 0.25.0
Add explenation for singleton resources to README.md
Fix msgpack version as 0.5.8 does not work on RBX.
Add 2.1.0 to travis
Specify rspec version do avoid loading 3.0.0.beta1 by dependencies
Manual install minitest to avoid failing bundle install on travis
Same for json 1.8.1 again...
Update to RSpec 3 and adjust/fix specs.
Manual gem require in specs and coverage only on CI or non-RBX
Add 2.1.0 to allowed failures due to interpreter bug. https://bugs.ruby-lang.org/issues/9315
Merge branch 'master' into feature/singleton

Conflicts:
	spec/spec_helper.rb