Add 'allowWindowsEscape' option

[frandiox]

@isaacs This is a minimum PR that fixes #50 #64 isaacs/node-glob#212 and maybe something else.

Since node-glob passes the options object directly to minimatch it shouldn't be necessary to update node-glob. It won't break existing code either since by default this flag is undefined. Basically if this is set, the caller have to make sure the provided string does not contain \ for path separator, only for escaping characters.

[andipavllo]

+1

[litmit]

Glob pattern is a some kind of language. It SHOULD be one for any platform.
I'm the Windows developer and don't see any working solutions for Windows at all. Therefore i fork minimatch and now happy (https://github.com/litmit/minimatch/tree/match-for-windows). It works as needed!. Don't modify pattern at all and only convert the path separator in file paths.

[isaacs]

This should still be done. Even if we aren't forcing \ to be a path separator in the pattern, we still need to make the path we're matching use / characters.

[isaacs]

This is a good step towards just not treating \ special in the pattern on Windows at all (ie, making this the only behavior starting with the next major after this.)