Improve maintainability score to A

[grgur]

Current maintainability score is B. Code climate shows how to improve that score here: https://codeclimate.com/github/ModusCreateOrg/budgeting

Let's get that A!

[nelsonomuto]

one of the things required is a codeclimate config to ignore the flow-typed directory

[nelsonomuto]

that reduces the number of files being analyzed from over 240 to 177.

then there are a few invalid "duplication" issues being raised, those need to be marked invalid; mostly with regards to the unit tests.

after this it reduces the amount of issues drastically

[nelsonomuto]

@grgur
I don't have access to the Code Climate as a member so I can't mark anything as "invalid" but here is a link to my code climate report https://codeclimate.com/github/nelsonomuto/budgeting

Here's a PR to add the .codeclimate.yml config to exclude the flow-typed directory: #201

[grgur]

@nelsonomuto thank you so much for contributing! This gets us a lot closer to the target https://codeclimate.com/github/ModusCreateOrg/budgeting

I believe the other improvements fall into the fun re-org category :)