[bug 1202288] Update translation-related reqs

[willkg]

This updates translation-related requirements to recent, supported
versions.

• Babel: 1.3 -> 2.0
• dennis: 0.4.3 -> 0.6.1
• polib: 1.0.3 -> 1.0.7
• pytz: 2013.9 -> 2015.4
• translate-toolkit: 1.11.0 -> 1.13.0

Also, I moved the following from vendor/packages/ to vendor/src/:

• Babel
• click
• translate-toolkit

[willkg]

These are all translation-related requirements that needed updating. To test them, I did the following:

1. ran the unit tests
2. ran the smoke tests
3. ran ./manage.py extract and ./manage.py merge
4. ran ./manage.py lint --errorsonly locale/
5. create a fresh vagrant vm and run all the above in the vm except smoketests

Pretty sure that covers all the bases here. There were no code changes--just version updates. The diff is mostly me removing stuff from vendor/packages/.

I'm going to wait for Travis to greenlight this, then merge it and push it.

[willkg]

Green! Merging.