MRI SQL Server support

I'm putting off trying to get the postgres and mysql jruby integration passing all the specs; I've gotten it working with sql server in jruby as that is what we use, but it seems pointless to add it  your library without the other two adapters working in jruby.

Currently, the sql server specs have to be run manually due to sql server not being installable on travis. I tagged the adapter specs to allow for them to be run individually and to exclude the sql server ones from running on travis.