Add Cargo.lock to the .gitignore.
Merge pull request #2 from steveklabnik/ignore

Add Cargo.lock to the .gitignore.
Move to sized types.

u32 is good for versions, but build numbers often appear as dates, which
are much larger.
Move parse result to Result

Result is better than Option in this case.
Naïve port of version requirements from Cargo
Break into sub-modules
Move tests into a module.
Remove unused exports