Add ability to create a ReflectionFunction from a closure

[asgrim]

Currently, because we don't load "live" (loaded-into-memory) code, we can't create a ReflectionFunction using a closure (because we actually don't have source code for it, thus can't create the AST from it). #36 may help to implement this, but because we don't have source code for closures, I'm not even sure if this is possible (without using core Reflection API and hacking it in...?)

[asgrim]

can use https://github.com/jeremeamia/super_closure for this

[asgrim]

though depends on jeremeamia/super_closure#70 to be compatible

[asgrim]

Handled by #151