Parser accepts invalid points

[perliedman]

Not sure if it's in the scope of this lib, but it currently accepts invalid point entries, which in turn makes it spit out invalid GeoJSON.

Sample input:

POLYGON(1,2,3)

results in:

{"type":"Polygon","coordinates":[[[1],[2],[3]]]}

From the PDF that shall not be mentioned, it appears that the grammar says a point must have at least x and y, possibly also z.

[tmcw]

Fixed in #24