PEP8-compliant changes in `test_event.py`

I changed a few of non-PEP8 "mistakes":
* too many blank lines before method definition
* wrong indentation of arguments in long arguments lists
* missing spaces around commas
Test event's notes

I added following tests that make sure event notes work correctly:
* test for notes field default value and emptiness (must not be NULL,
  but can be empty, ie. `""`)
* test for notes being saved correctly
Test site's notes

I added following tests that make sure site notes work correctly:
* test for notes field default value and emptiness (must not be NULL,
  but can be empty, ie. `""`)
* test for notes being saved correctly

Additionally I removed docstring from `setUp` method for
`TestEventNotes` test case because it didn't fit and I couldn't come up
with a better one.
I decided to remove it because most people looking into unit-tests will
know what `setUp` is for.
Merge pull request #109 from pbanaszkiewicz/testnotes

Tests for notes in Site and Event models