docs: fix a few simple typos

[tobiasmcnulty]

There are small typos in:

• docs/releases/0.13.0.rst
• docs/topics/deployment/paas.rst
• docs/topics/deployment/telecom.rst
• docs/topics/extensible-models.rst
• docs/topics/i18n.rst
• docs/topics/testing.rst
• rapidsms/contrib/httptester/views.py
• rapidsms/contrib/messaging/static/messaging/javascripts/jquery.simplyCountable.js
• rapidsms/router/blocking/router.py
• rapidsms/router/db/router.py
• rapidsms/router/db/tasks.py
• rapidsms/router/db/tests.py
• rapidsms/tests/test_management.py

Fixes:

• Should read occurred rather than occured.
• Should read instantiate rather than instaniate.
• Should read simplicity rather than simplicitiy.
• Should read receive rather than recieve.
• Should read outgoing rather than outoing.
• Should read module rather than modeule.
• Should read milliseconds rather than miliseconds.
• Should read message rather than meessage.
• Should read management rather than managment.
• Should read infrastructure rather than infrastructre.
• Should read explicitly rather than explicity.
• Should read existing rather than exisitng.
• Should read deployed rather than deploayed.
• Should read contacts rather than contactcs.

Closes #494