Add support for API versioning

[mikkoseppa]

• Refactor Route to support multiple handlers and api versioning.
• Add HeaderApiVersioning and RouteApiVersioning features.
• Refactor Router to forward apiVersioningConfig from Router's config to Route.
• Also resolve feature name in Router to the actual versioning feature.
• Add tests for Router and both versioning features.

[coveralls]

Coverage decreased (-0.1%) to 95.887% when pulling 9303cd971f9c20f84db9365ca286ce28665c70dd on mikkoseppa:ms-add-support-for-api-versioning into c67141198e16d3edcf1157e6d0c684fe77d17771 on Vincit:master.

[coveralls]

Coverage decreased (-0.1%) to 95.887% when pulling 9303cd971f9c20f84db9365ca286ce28665c70dd on mikkoseppa:ms-add-support-for-api-versioning into c67141198e16d3edcf1157e6d0c684fe77d17771 on Vincit:master.

[coveralls]

Coverage decreased (-0.1%) to 95.887% when pulling 9303cd971f9c20f84db9365ca286ce28665c70dd on mikkoseppa:ms-add-support-for-api-versioning into c67141198e16d3edcf1157e6d0c684fe77d17771 on Vincit:master.

[coveralls]

Coverage decreased (-0.1%) to 95.887% when pulling 9303cd971f9c20f84db9365ca286ce28665c70dd on mikkoseppa:ms-add-support-for-api-versioning into c67141198e16d3edcf1157e6d0c684fe77d17771 on Vincit:master.

[coveralls]

Coverage decreased (-36.7%) to 59.283% when pulling 706d4dd61eb5fea830a729e1cc062a9acc3e09b9 on mikkoseppa:ms-add-support-for-api-versioning into c67141198e16d3edcf1157e6d0c684fe77d17771 on Vincit:master.

[elhigu]

We could remove older than 6 node versions from travis

TypeError: availableApiVersions.includes is not a function

[elhigu]

Could you still drop node .12 from .travis.yml file to make tests pass?