Bump version to 0.2.1 and upgrade pip version

[rafaelreuber]

I think is time to bump version to 0.2.1 and upgrade pip version.

Important issues was fixed such as:

• All tasks execution stops when one task hits it's "max_run_count" value All tasks execution stops when one task hits it's "max_run_count" value #55
• Enabled tasks do not run when there is another schedule entry which is disabled Enabled tasks do not run when there is another schedule entry which is disabled #37
• Fix date_changed is not updated when PeriodicTask instance is saved fa8dfef