Human readable config errors

[avara1986]

Show more help information if the config file not have a good structure with error messages like

Config file must start with `pyms` keyword, for example:
    pyms:
      services:
        metrics: true
        requests:
          data: data
        swagger:
          path: ""
          file: "swagger.yaml"
        tracer:
          client: "jaeger"
          host: "localhost"
          component_name: "Python Microservice"
      config:
        DEBUG: true
        TESTING: true

[coveralls]

Coverage increased (+0.01%) to 99.71% when pulling 2ca9652 on feature/human_readable_config_errors into e70f4be on master.

[alexppg]

LGTM, this sure will be helpful.

[avara1986]

@alvarolinarescabre suggested this change 😉