Finishes #63 #64

* Remove half baked CallFn implementation.
* Cleanup whitespace
* Cleanup read/write mem functions

Process is an incorrect name for the DebuggedProcess struct that the
thread is "a part" of. Also, no need to export that field.

* Properly find next source line for goroutines blocked in chanrecv
* Refactor breakpoint clearing
* Refactor temp breakpoint setting

* DebuggedProcess method: `PrintGoroutinesInfo` -> `GoroutinesInfo`
* `goroutines` command in command/command.go now responsible for
  printing info.

* Better tracking of current goroutine
* More efficient, eliminates superfluous step syscalls
* Handles concurrency and thread coordination better

There were certain instances where the calculation of the stack frame
was incorrect, causing for garbage to be returned by a print command.

when evaluating a nil pointer.