Add local_caller method
Sometimes you want a stack trace of what chain of methods invoked
wherever you are right now. `caller` does this, but it also includes
things like library and irb/pry frames in the stack. Often what I want
is the stack frames from whatever code is in the current code base.
`local_caller` uses the current directory as a proxy for "current code
base". It `select`s the frames that contain `Dir.pwd` which leaves us
with a nice, small stack trace.
This is on `Kernel` so it can be uses anywhere.