Can't create snippets under special characters

[joereynolds]

If we have a file named _php_$ and we try and type $<tab>, it does not expand.
It seems (from my basic use of it) that it only works on characters [a-z]?

[LemonBoy]

The pattern on this line [1] should be modified by replacing \w with \f, after all we're building a path to the snippet file.

[1] https://github.com/KeyboardFire/vim-minisnip/blob/master/plugin/vim-minisnip.vim#L14

[joereynolds]

FYI this is fixed in my fork