Letting the package consider .jsbeautifyrc files as well

I have my private settings, set in sublime, but it often happens that I work on external projects that have their own formatting rules. A .jsbeautifyrc file is the natural choice for shared projects, so I figured it would be great if the package would also consider them, if present.

The settings are now augmented in a sequential manner:
* JsBeautify default options
* sublime settings (indentation)
* sublime setting file(s)
* .jsbeautifyrc files (starting from root down to path of modified file, like the node cli tool does)

As a minor modification, the package doesn't set its own hardcoded defaults anymore; I expect them to be set by JsBeautify itself quite reasonably.

General note: This is a 'suggestion' pull request. I haven't programmed in Python before, so, this is the result of my inference from various other snippets and online learning this afternoon. If some bits are done way better in a different way, I'd be happy to know about that.