full visitor pattern withh double dispatch
strong typing based on interface, not object
documentation (commiting now from Guadeloupe)
some comments and refactoring for D.R.Y
PSR-0 compliance
unit testing with PHPUnit
some explanations
PSR-0 compliance
unit test
Added php 5.3 & 5.4 to travis config
Added docblocs to User entity
Updated mapper with docblocs & removed unused (unreachable) code
Updated docblocs for mapper test
Removed _ for protected property in data mapper
Merge pull request #30 from eddiejaoude/master

Data mapper improvements inc. docblocs, unused code etc
Cleaned up code to be consistent, inc. adding docblocs, using PSR naming conventions & typos

Docblocs benefits:
- IDE auto complete gives info on type etc
- Auto documentation on CI
renamed README
refactored README
Merge remote-tracking branch 'Trismegiste/unit-test-for-singleton'
Merge remote-tracking branch 'Trismegiste/unit-test-for-observer'