Prevent rigged files from importing themselves

[isochronous]

add a check in the _getSingle method to compare a file being imported to
the file doing the importing. If they match exactly, do not import it,
as the file would be importing itself. This is an effort to fix #25 .

[isochronous]

Actually, this isn't ready to go yet, as imported files that import their own directories still import themselves. Need to work on this a little bit more.

[isochronous]

I couldn't ever really get this working properly, and I found another package (https://github.com/timrwood/includer) that did the same thing without all these problems.

[DamonOehlman]

Cool thanks for the heads up on includer. I might make a mention of that here, given I pretty much always use browserify these days.