Improve states readability with binary literrals

[nfroidure]

The parser states can now be expressed with the binary litteral operator:
https://github.com/nfroidure/svg-pathdata/blob/master/src/SVGPathDataParser.ts#L530-L541
http://2ality.com/2015/04/numbers-math-es6.html

[NaridaL]

It's not quite clear to me why they're implemented as a bit mask anyway, apart from the relative flag, all the other states are mutually exclusive?

[nfroidure]

These states are also used and stored in the same variabl by the parser https://github.com/nfroidure/svg-pathdata/blob/master/src/SVGPathDataParser.ts#L511-L525

That said, the bit mask was really necessary to store the parser state, it doesn't save that much memory.

[NaridaL]

You can do it with no explicit state var at all :-P https://github.com/nfroidure/svg-pathdata/blob/simpler-parser/src/SVGPathDataParser.ts