rangelib.py: Add parse_raw() method.

parse_raw() parses a string generated by RangeSet.to_string_raw().

>>> RangeSet.parse_raw(RangeSet("0-9").to_string_raw())
<RangeSet("0-9")>

Change-Id: Ia74daa30476d5e9ad73c368f4ecc64c755b734a5
2 files changed