Merge features from dev to master

Features:

• Added pseudo-hash to filename. Closes #3 (closed).
• Updated documentation in README. Closes #4 (closed).

Changes:

• Changed --print-src to --print-source

Breakage:

• dd12de30 changes the filename of newly downloaded videos and subsequently re-downloads are only prevented if the video on disk already has the new filename. Therefore, this will cause a re-download of all recordings specified by you if you rely solely on existing filenames to prevent downloading old videos again. Users making use of the history file via --history will not be affected.
• 213e77a7 will break any automated scripts making use of --print-src. Make sure to update them to use --print-source if you make use of this flag!