fix unhandled traceback on "pynag config --remove"

* Help screen provided incorrect syntax, correct syntax is "pynag config --remove key [--old_value=specific_value]"
* Syntax was NOT supposed to be pynag config --remove key=specific_value
* Closes #32
* Added unittests to make sure Parsers.config._edit_static_file behavior does not change
docstring improvements

* Better explain arguments and what they do
* name argument is unused, but is left here intentionally for compatibility reasons
* Closes #31
Removed redundant __init__()

Was causing unhandled traceback as it makes pynagerror not behave like Exception should.
Change from eventhandlererror to pynagerror in experimental gitrepo code
Changed test suites for build tests
Switch from BaseException to PynagError