Fixed bug where whitespace wasn't trimmed from keys.

Went back to MSTest to stay consistent with existing tests.

- Added unit tests for various key/value whitespace scenarios.
- Removed unnecessary AssemblyKeyFile attribute which prevented usage of InternalsVisibleTo for unit testing purposes.
Edit IniPatternsTest to use the style of the project.

- Move "using" statements above "namespace" one.
- Merge individual tests into one, convert instance fields into locals.
- Change tests to work against IniDocument instead of internal IniPatterns.
Fix the setting key whitespace problem by correcting the regular expression instead of calling Trim().
Merge branch 'trim-white-space-on-keys'