Add AbstractRetriever and remove duplicate implementations through inheritence
Add coverage directory and IDE files to gitignore
Remove tabs/whitespace. Add unit test coverage. Add code comments.
Add docs make linkcheck to travis-ci
Add travis-ci install docs dependencies
Add travis-ci install docs dependencies
Add PHPDocumentor 2 to travis-ci
Merge with upstream master
Merge with upstream master branch.
Merge pull request #68 from webdevel/travis-ci-dev

Add Sphinx Doc and PHPDocumentor to Travis-CI