Add str::trim. Fixes #28.
Add str::trim. Fixes #28.

Also, changed the strip-related functions to take a str val instead of a
proper lily value. This allows str::trim to create a fake str val to pass to
the strip functions as helpers.

jesserayadkins/lily,FascinatedBox/lily,jesserayadkins/lily,FascinatedBox/lily,FascinatedBox/lily,FascinatedBox/lily,jesserayadkins/lily