Added delete methods to the different backends so that applications can delete a set password.
Fixed stupid issues in Mac OS X extension (forgot a ; and removed and unused var). Added delete_password as a global func from keyring.
Added tests for new methods.
Added content to README and CONTRIBUTORS
Fixed compilation issue mac os x.
Fixed segfault.
Ensure that we are passing the e.
Ensure we have all rights.
Merged with trunk and implemented os x code using ctypes.

--HG--
rename : README.txt => README
Fixed tests.
Set kwallet to be none.
Added reason to reduce the diff.
Add explaination when unable to delete a password + cleanups
Added cli delete option.
merged with parent.
Merged with trunk and fixed all the different conflicts.
Fixed most of the pep8 errors of the code base.
Merged with trunk.
Remove the try import that has not point.
Refactored OSXKeychain implementation to be consistent with other pure-python keyrings.