* 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

Also refactored code a bit, removed printing functions from proctl
package and inlined them into command.

FDEs previously were loaded into a red/black tree and searched. This is
significantly more expensive than a binary search over a slice. Not sure
what I was thinking using a red/black tree - this binary search
implementation is significantly more efficient.

This commit fixes a race condition between Delve and the runtime of the traced process. When a new thread is created in the traced process, Delve takes note of it and then continue both the new thread, and the thread that called clone. If Delve attempts to use data in `runtime.allm` before the new `m->procid` is set, errors occur. The errors are due to Delve assuming any m with a procid of 0 is the main thread of the process (due to how theGo runtime allocates M's, only `clone`d threads have procid properly set. This causes certain events (like `next`) to happen twice to the main thread, because 2 m's in `runtime.allm` have a `procid` of 0, and also causes various other issues that prevent proper thread coordination from Delve.

Fixes #43

As of go version 1.4 the standard library syscall package is "locked
down" and code outside of the standard library is recommended to migrate
to the go.sys subrepository.

Reference: https://golang.org/s/go1.4-syscall

Currently there is no need for the other items in the ProcessStatus
struct, we really only care if the process is not running, so we can
avoid sending signals to it.

Currently only works for amd64 processors.

Handle SIGINT by stopping the traced program and then displaying a
prompt to the user for commands. If the traced process is not running,
this is a noop.

Closes #30

This remove reliance on the procfs for figuring out what threads are
already active when we attach to a running process. The allm linked list
will be present to matter what OS we're on, whereas procfs will not be
present everywhere.

This is the first in a series of steps to support more platforms.