Bug fixes and test coverage updates.

Version 3.6.5

• Remove unittest2 dependency.
• Tests no longer run against Python 2.5.
• update(), delete() work on Application, Transcription and UsageTrigger
  instance classes.

Mobile

• Add support for filtering by mobile-enabled numbers in both IncomingPhoneNumbers and AvailablePhoneNumbers.
• Add support for filtering by all mobile, local, and toll free numbers in IncomingPhoneNumbers.