Enhancement to the Crystal client generator

Here is a list of pending enhancements.

remove commented code: some code (ruby) was commented out. If confirmed these code do not need to be plotted to Crystal, we can safely remove it
add return type to the function signature
add auto-generated doc (api, model, readme)
add more tests (e.g. upload file filie)
better code format

If anyone wants to help, please reply to let us know and we can share some good starting points.

Latest master