Py-ms

**New functionalities:**
* Memoizes config file per service
* Updates dependencies
* Created [metrics as a service](https://py-ms.readthedocs.io/en/latest/services/#metrics)

HELP flask_request_latency_seconds Flask Request Latency
TYPE flask_request_latency_seconds histogram

**New functionalities:**
- Removed tracer from core
- Created tracer as a service
- Configure tracer between jaeger and lightstep from config.yml
- Set tracer host from config.yml
- Check if package is installed

**Bugs fixed:**
- Fix Coveralls. Not push coverage since 07/2019
- Fix error when swagger service not present in config.yml

- Changed logging messages to debug
- Added pylint validation to CI

* Fix pypi dependencies

* Access to pyms class from `flask.current_app.ms`

* Added retry system to requests wrapper

* Fix pylint errors

* Updated docs