Added several docstrings
Added gitignore file
Removed mutable default argument in flatten

Used to have
flatten(obj, types=[], endianness='>').
Changed to
flatten(obj, types=None, endianness='>')
with if types is None: types = []
Added LRFloat to replace unitless LRValue
Clarified documentation on getType and flatten().
Updated flatten docstring and fixed LRValue.__le__

Previously LRValue('m').__le__(LRValue('s')) returned True. This allowed flatten to accept, for example, Value(1.0,'m') when the suggested types list consisted only of 'v[s]', which is clearly wrong.
Added note in parseNumber docstring that regexp should be used.
Do not allow 'v' as a type tag.

We require parseUnits to find brackets '[]'.
There may be nothing inside the brackets, indicating unitless number.

Also now require LRValue constructor to get a unit. None indicates unitless.
We force a unit of '' to turn into None, but will simply disallow the ''
case soon.
Removed 'v' and 'c' tests and added 'f'