Add passthrough and offset options (#14)

* Add passthrough and offset options

- Passthrough will send stream directly to VLC without processing in
  Streamlink. This is useful if user wants to seek within VLC. However,
  this will bypass Streamlinks ssl verify skip, and user will have to
  accept the cert in VLC to play the stream.
- Offset will offset the Live / VOD stream by the specified time. If
  live, offset is negative from current game time. This option works on
  `play`, `cast` and `record` commands

* fix CI for windows