Remove all paths from configuration

[raveclassic]

• replace pathsToSpec with a list of parsed spec objects

  • supports any spec format, not only json/yaml)
  • support for specs loaded from network or any other source, not only from disk

• return TFSEntity from generate instead of accepting out parameter

  • supports for any output format, not only writing to disk

• ~remove pathToPrettierConfig~

  • ~prettier should be a part of typescript language~ done in #51

• ~remove fileReader~

  • ~"files" are one of many possible sources and should be handled outside of the lib~ done in #51

[raveclassic]

swagger-parser supports automatic http/file spec resolution, we need to discuss if we really need to control it ourselves