Full support for all video players

Only works if CS50 2x has previously been run on the webpage, with the
exception of YouTube which always works
CS50 2x code fully integrated

Clicking extension once on a movie invokes CS50 2x and gets timestamp
(YouTube). For isites the timestamp is only retrieved on the second and
further clicks. Video is not paused on first click. Clicking extension
more than once will pause video, but may cause errors with CS50 2x.
Potentially local storage could be used to keep track of use of
extension per webpage?
Buttons work

Buttons work to cause CS50 2X or pause-video/get-timestamp to execute.
Remains to do: CS50 2x resets time with respect to original video
(probably unavoidable since we don't have API access to original video),
and timestamps are currently locally stored within  the inner js, not
html
Milestone 2.0

- Finalized Save/Edit function
- Implemented synchronized local storage (still buggy across two
simultaneous windows)
- Added CSS for notepad.html and popup.html
- Preparations for integrating video javascript functionality in version
0.3.0
- Updated manifest version to 0.2.0
Merge remote-tracking branch 'origin/pause-video'
Merge remote-tracking branch 'origin/upload-function'