Translation endpoint
GET /api/translate?engine=google&from=auto&to=en&text="sonrisa"
Get a JSON array of supported source and target languages for a particular engine
GET /api/source_languages?engine=google
GET /api/target_languages?engine=google
Obtain text-to-speech audio files from an engine, provided said engine supports them
GET /api/tts?engine=google&lang=en&text="hi"
Switch between source and target languages, as long as the source language isn't "auto"