Moved xpath into boostrap java

And removed complex-find while at it.

Submitting to @bootstraponline for review.

I'm working now on changing the getPageSource code to reuse the same code here.
stack would be nice here and elsewhere you follow this pattern.

Here's a nice little function I found on SO (untested) to get the stack as a string

http://stackoverflow.com/a/10137518

You could make something similar a method (override toString, maybe?) of your custome exceptions.