Rewrite backend to use mongo instead of in memory data

[codeclimate[bot]]

Code Climate has analyzed commit a3025d7c and detected 21 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	5
Duplication	16

The test coverage on the diff in this pull request is 38.1% (50% is the threshold).

This pull request will bring the total coverage in the repository to 30.7% (4.6% change).

View more on Code Climate.