Moved plexapi import into setup_platform().

Changed CONTRIBUTING.md to refer to requirements_all.txt instead of requirements.txt

CONTRIBUTING.md

@@ -18,7 +18,7 @@ For help on building your component, please see the [developer documentation](ht
 After you finish adding support for your device:
 
  - Update the supported devices in the `README.md` file.
- - Add any new dependencies to `requirements.txt`.
+ - Add any new dependencies to `requirements_all.txt`. There is no ordering right now, so just add it to the end.
  - Update the `.coveragerc` file.
  - Provide some documentation for [home-assistant.io](https://home-assistant.io/). The documentation is handled in a separate [git repository](https://github.com/balloob/home-assistant.io).
  - Make sure all your code passes Pylint and flake8 (PEP8 and some more) validation. To generate reports, run `pylint homeassistant > pylint.txt` and `flake8 homeassistant --exclude bower_components,external > flake8.txt`.

homeassistant/components/media_player/plex.py

@@ -36,7 +36,6 @@ from homeassistant.components.media_player import (
     SUPPORT_NEXT_TRACK, MEDIA_TYPE_TVSHOW, MEDIA_TYPE_VIDEO)
 from homeassistant.const import (
     STATE_IDLE, STATE_PLAYING, STATE_PAUSED, STATE_UNKNOWN)
-from plexapi.myplex import MyPlexUser
 
 REQUIREMENTS = ['https://github.com/miniconfig/python-plexapi/archive/'
                 '437e36dca3b7780dc0cb73941d662302c0cd2fa9.zip'
@@ -52,6 +51,7 @@ SUPPORT_PLEX = SUPPORT_PAUSE | SUPPORT_PREVIOUS_TRACK | SUPPORT_NEXT_TRACK
 
 def setup_platform(hass, config, add_devices, discovery_info=None):
     """ Sets up the plex platform. """
+    from plexapi.myplex import MyPlexUser
     name = config.get('name', '')
     user = config.get('user', '')
     password = config.get('password', '')