Add copy of GNU GLP v3

The actual license has been missing for a while, now it's there.
Shorten documentation boilerplate

Text mentioning the noweb documentation was still in the individual comments; they've
been removed.
Add argument to use scientific notation

The '6e-5' notation is pretty crappy in tables; this commit adds an argument to set it,
with `FALSE` the default.
Reformat whitespace and source code for booktabs.R
Release version 0.3.3

* Add flag to remove scientific notation from 'booktabs' tables.
* Clean up some of the boilerplate documentation at the top of each
  source file
* Add a copy of the GPL