DEV: Refactoring MS for BIT integration

**Is your feature request related to a problem? Please describe.**
To achieve the target of 2 REST APIs (MS and BIT APIs) with one database (bit_schema database), MS schema needs to be refactored to accommodate BIT.

**Describe the solution you'd like**
- [ ] Refactor one of the UserModel field from `organization` to `current_organization` to remove ambiguity with `Organization` table reference used in BridgeInTech schema.
- [ ] Refactor the use of Float to Numeric with precision "16,6" so to avoid precision mismatch from data store/retrieve from db.
- [ ] modify `.travis.yml` to employ postgresql as db for testing on travis build
- [ ] add pytest-cov dependency in requirements.txt

**Describe alternatives you've considered**
NA

**Additional context**
This is a cross-project issue between MS and BIT where improvement will be made gradually throughout GSoC 2020 period.