Compatibility with Mongoid 3
Start mongodb on travisci
Add appraisals to test both Mongoid 2 and 3
Add backwards compatibility with Mongoid 2
Move away from Jeweler because it doesn't work with Appraisals and Gemfile groups
update travis build matrix
exclude 1.9.2 with mongoid3
Add changelog to README [ci skip]
Dont use bson_ext on jruby