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.
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
