Allow run functions to accept pathlib.Path objects

[aloukina]

This PR addresses #384.

• I refactored the code since the input processing part was shared by all components: this is now done via Configuration Parser method.
• The path to the config file can be passed as either string or pathlib.Path object. Previously the latter functionality was available as undocumented option.
• I didn't add new tests for that method since the functionality is already tested in tests we wrote for individual components

[pep8speaks]

Hello @aloukina! Thanks for updating this PR.

• In the file rsmtool/configuration_parser.py:

Line 1416:101: E501 line too long (103 > 100 characters)
Line 1422:101: E501 line too long (105 > 100 characters)

Comment last updated at 2020-02-26 20:10:10 UTC

[coveralls]

Coverage increased (+0.05%) to 90.233% when pulling d8bf8f0 on 384-allow-run-functions-to-accept-Path into 0eb9a96 on master.

[desilinguist]

I haven't reviewed the details but had a more overarching comment that'd be good to think about now.

[desilinguist]

Hmm, might it make more sense to just move this logic to the ConfigurationParser() initializer instead of having this classmethod since all we are doing is getting the args and then calling the initializer anyway?