Ignore spaces

Ignore spaces

We add the spaces `Parser` which returns nothing `()` and skips any
spaces.

`spaces` is already defined in Parsec, but does not do exactly what we
want, we can hide it from the import.

`skipMany a` matches 0 or more `a` and skips them.

`>>` is the **bind** operator. It may have completely different meanings
depending on the monad you use. In the Parser monad in means "try the
first parameter, then try the second with anything that is left", i.e.
"first skip all the spaces, then match the symbol".