Fix path split.
Merge pull request #367 from DeaR/fix-path-split

Fix path split

path split by , , if fails error of included path of (whitespace) or ,.

:help path

Spaces can also be used to separate directory names (for backwards
compatibility with version 3.0). To have a space in a directory
name, precede it with an extra backslash, and escape the space:

:set path=.,/dir/with\\\ space
To include a comma in a directory name precede it with an extra
backslash:

:set path=.,/dir/with\\,comma