Unpin pycrypto. Bump version.

Package versions in Python packages (especially libraries) should not be pinned down. Two specific reasons why `jose` shouldn't do it:

1. It doesn't look like it uses any specific functionality of version pycrypto 2.6. On the other hand it causes serious compatibility problems:
  `pkg_resources.VersionConflict: pycrypto 2.6.1 is installed but pycrypto==2.6 is required by ['jose']`

2. [pycrypto 2.6.1 fixes an important security bug](https://github.com/dlitz/pycrypto/blob/af058ee6f5da391a05275470ab4a4a96aa22b350/ChangeLog).

Please merge and upload new package to PyPI. Thanks :)