Make integration test for linter web service

[amrondonp]

Unit tests for this service are written. However, as this application has so many dependencies, we need to make an integration test (in travis) that would be something like:

1. Create 3+ test cases for the languages we support
2. Update the travis CI configuration so that it
   2.1. Build the service in the docker environment
   2.2. Makes an HTTP call for each of the test cases
   2.3 Verifies that the outputs are being shown correctly
   2.4 Runs on every pull request