Remove devise + devise-encryptable from Gemfile

They are specified in gemspec
Reference correct CommonRake location
Correct requires for testing_support in spec_helper
need to depend on 2.0.0.beta so people stop trying to use master branch for Spree versions that are != 2
Add instructions to README for 1-3-stable and 1-2-stable brancheS
Remove Mass Assignment of Role IDs