Add copyright notices.

Closes #3
Add copyright notice to individual files. Related to #3
Merge pull request #5 from gwillen/master

Add LC_ALL=C to convince sed more firmly to use bytes.
Update README

Note the original decks are dead links now

credit to gwillen
Update README.rst

Include link to http://www.mnemosyne-proj.org/ the first time it's mentioned.
Detect and correct input file format errors

The question pool files have lots of formatting errors in them. Some we already
catch and fix automatically. For the rest, we now detect and print them while
parsing the file.

Rather than update the script to fix every conceivable error, we'll just edit
the input files to fix the handful that appear.