Make LibraryImporter a little more robust

...alternative title, "Let me import UnfoldingMaps because I want to use it in a demonstration tomorrow."
Partially addresses [#85](https://github.com/jdf/Processing.py-Bugs/issues/85) and [#86](https://github.com/jdf/Processing.py-Bugs/issues/86), by allowing LibraryImporter to skip over things it knows will be problematic, and to recover when imports don't work. It's probably a little too permissive, but I want to err on the side of libraries *mostly* working for now.
UnfoldingMaps has a single class that depends on TUIO. Since classes are lazily initialized in Java, if you don't use that class, you can not have TUIO and your sketch will run fine. When we try to explicitly import it in jython, though, it gets initialized and throws a NoClassDefFoundException.
I'm not sure how widely that sort of thing happens, though. I can go through the available processing libraries to find out.