Use an integer to store ES port

using a string was crashing the requests lib
Install requests
Compat unicode
Catch connection exception on document index / remove
Typo
Remove cache clearing methods

Document lists is not cached anymore, since it comes from ES. There is
no need to clear the cache anymore upon document modification.
Save document when revision is saved
Add parameter to conditional save document with revision
Use tasks for ES communication
Define a better serializer for json
Correct function call in mapping command
Pass all required parameters to ES signals
Fix signals tests

Fixes #29