add Mongoid 4 models
mongoid4 is on current github master branch
update files to support new mongoid4 orm variable
update dummy app with mongoid4
add exclusion variables to build matrix
update README
increase string length (from rails default of 255) to 2048 for redirect_uri columns to accommodate longer URIs; 2048 selected by consulting http://stackoverflow.com/questions/417142/what-is-the-maximum-length-of-a-url and picking a power of two
Refactored how expires_in is returned to clients, it now represents the token TTL from the time the response is sent
According to Section 4.2.2 of the OAuth spec (http://tools.ietf.org/html/rfc6749#section-4.2.2):

expires_in
         RECOMMENDED.  The lifetime in seconds of the access token.  For
         example, the value "3600" denotes that the access token will
         expire in one hour from the time the response was generated.
         If omitted, the authorization server SHOULD provide the
         expiration time via other means or document the default value.

The current implementation returns the values of the `expires_in` fields on the token record, which is relative to
the time the token was generated.  This change switches to returning the expiration time relative to when the request
was made (since future requests could return the same token as long as it's not expired).
Do not try to load unavailable Request class for the current phase.

If you send grant_type=code for token request for example, you'll see
runtime exceptions such as:

  undefined method `pre_auth'; for #<Doorkeeper::TokensController:0x007fe04b7aa778>

Since grant_type comes as a request parameter, it's better to
explicitly limit the available request implementations rather than
trying to load the class and rescue constant lookup failures.
Update README.md
Revert "Update README.md"

This reverts commit b47c625b0484c8c8fb46f568501cdb5b647b79e6.
Fixed deprecation warning: has_many :conditions option
has_many rails 3 and 4 compatibility
resolved naming conflict with Doorkeeper::Rails module
Remove Ruby 1.8.7 from travis, add 2.0.0 to README
Trailing white space and Ruby 1.9 hash syntax
"warning: `*' interpreted as argument prefix"
README update
"warning: `&' interpreted as argument prefix"
"warning: assigned but unused variable - e"