extend dill.source.getsource for non-function-like objects

[mmckerns]

dill.source.getsource is pretty good about getting the source for imported and interactively defined function, lambdas, and class methods. It'd be nice to get the source code for classes and class instances and such. Currently, assumes the inspected object has a func_code attribute.

[mmckerns]

getblocks and getsource can grab class code (from file or interpreter) as of e67781b. getblocks can also get the class source for class instances, but not the constructor for the instance. getsource can get the class source and the constructor for instances if there's a nice repr for the instance… otherwise it raises an AttributeError (intentionally). Is this good? Not sure.