[WIP] beginnings of websocket support
completed basic rpc implementation
move common websocket code to bixby-common
rename websocket dir to api
extracted API handler code to separate class
use generic 'request' instead of http_request
renamed tests to signed
cleanup
pass handler class, not instance
simple API.version method used for testing
support signed WebSocket requests

* also fixed bug when calling methods that take no args
* bit of cleanup/refactoring
rename files
use custom api-auth