vcs: Add title to exercises.rst
The title is required for it to appear in the index file of sphinx.
http://www.stallman.org%Richard Stallman
http://www.catb.org/~esr/%Eric Raymond
http://ianmurdock.com/%Ian Murdock
http://lessig.org%Lawrence Lessig
http://torvalds-family.blogspot.com/%Linus Torvalds
http://www.python.org/~guido/%Guido van Rossum
http://www.wall.org/~larry/%Larry Wall