Fix wrong redirect following authorization step, refs #171

Fix for #163 (https://github.com/bshaffer/oauth2-server-php/issues/163) allowed
authorize flow to handle `redirect_uri` as an optional parameter. The change
resulted in user not being redirected back to the client after granting or
denying client's access.

This fix verifies whether `redirect_uri` is set or not in
`OAuth2\Controller\AuthorizeController`'s `handleAuthorizeRequest()` method.
If it's not set, it grabs the client's registered value.

If/When support for PHP 5.3 is dropped, the code can be modified to
`$this->clientStorage->getClientDetails($this->client_id)['redirect_uri']`.
Add unit test to check redirect_uri value, refs #171, refs #163
Merge pull request #171 from davidkuridza/fix-redirect-in-authorization-flow

Fix wrong redirect following authorization step
adds mongo tests back since this is fixed:  https://github.com/travis-ci/travis-build/issues/87
Merge branch 'develop' of https://github.com/bshaffer/oauth2-server-php into develop
Revert "adds mongo tests back since this is fixed:  https://github.com/travis-ci/travis-build/issues/87"

This reverts commit 5fcd6c29e8cecc58049076fcb4e4f1dc97020d1d.
fixes #190 - validates client credentials before grant type
fixes #191 - passes config to HttpBasic
moves documentation to github pages
fixes #194 - makes some appropriate properties protected instead of private
fix undefined classes.
fixes #192 - reference errors and adds tests