Fix RFC822 filters + More tests (#257)

* Make rfc822 filters compatible with Windows systems.

.strftime() is relative to the system it's being run on.
UNIX has '%s' for seconds since the EPOCH, Windows doesn't (ValueError).
Solution: use .timestamp() to achieve the same result on both platforms.
This also allows us to drop the float() around it, since it returns a float.

* Start testing filters

* Add placeholders for more tests

* Make 'tests' folder a Python package

Now you can run tests with just `pytest tests`

* Update readme and travis config

* Test timesince()

* Update and organize .gitignore

Deleted: (nothing)
Added: Coverage files, .idea\

* Test filter_truthy, category_name

* Tests for backend.py

* Tests for bencode.py

* Move (empty) test_models.py to tests package

* Tests for utils.py

* Fixes for flattenDict

* Change name to `flatten_dict`
* `newkey` was assigned but never used

* Add a helper class for testing

* Show coverage on Travis

(only Travis for now...)

* Remove IDE

* Use correct assert functions

* Update README.md

README.md

@@ -11,9 +11,9 @@ It's not impossible to run Nyaa on Windows, but this guide doesn't focus on that
 - Other than PEP8, try to keep your code clean and easy to understand, as well. It's only polite!
 
 ### Running Tests
-We have some basic tests that check if each page can render correctly. To run the tests:
+The `tests` folder contains tests for the the `nyaa` module and the webserver. To run the tests:
 - Make sure that you are in the python virtual environment.
-- Run `python -m pytest tests/` while in the repository directory.
+- Run `pytest tests` while in the repository directory.
 
 ### Setting up Pyenv
 pyenv eases the use of different Python versions, and as not all Linux distros offer 3.6 packages, it's right up our alley.