Support pages ordering in admin

* Pages ordering is supported via django-orderable.
* Add jQuery library.
* Add jQuery UI library.
Remove lettuce integration

* Lettuce was a fun experiment, but has no continuous use in this
project.
* Remove unused requirements.
* Remove unnecessary code from comments template tags.
* Code coverage is now at 100%.
* Clean up Fabric settings.
* A side note, to install pycrypto some machines require running
`export CFLAGS=-Qunused-arguments` and
`export CPPFLAFS=-Qunused-arguments`.