PEP8 fixups and code refactorization

Following multiple PEP8 hints to make code look nice.
Remove template file

We no longer need it as the ADFS request is now builded as a
etree.Element object which can be easily stringified.
Fix typo: PRoviders -> Providers.
Send serialized RequestSecurityToken object.

Serialize RequestSecurityToken object before sending it to the ADFS
server, instead of sendin raw etree.Element object.
Rename main.py to adfs-client
Update README.md file.
Add Usage section to README.md.
Disable --cookie options.
Merge pull request #1 from zaccone/dev

Working implementation.