Handle multibyte chars in Tokenizer.

Previously the tokenizer crashed in Ruby 1.9 when unicode characters
present in input, because the scan pointer was advanced by string
length, which in Ruby 1.8 is the length in bytes, but in 1.9 is
the length of chars.

Now using #bytesize method in Ruby 1.9+.
Simplify :S token regex.

Ruby 1.9 printed a warning for the old regex.

Using just \s is enough to match all whitespace.
Bump version to 0.0.2.