Wire in pprof handlers.

Based on http://stackoverflow.com/questions/19591065/profiling-go-web-application-built-with-gorillas-mux-with-net-http-pprof

Tested using `docker -d -D -H=unix:///var/run/docker.sock -H=tcp://127.0.0.1:4343` then running the following in parallel (you need to generate load in order for pprof to work!).

```
go tool pprof http://localhost:4343/debug/pprof/profile
```

and 

```
for i in $(seq 1 40); do docker run -d -t busybox sleep 600; done && docker ps
```

Sample output:

```
Total: 46 samples
      17  37.0%  37.0%       20  43.5% syscall.Syscall
       9  19.6%  56.5%        9  19.6% 0x00007fff647f48a2
       7  15.2%  71.7%        7  15.2% runtime.usleep
       6  13.0%  84.8%        6  13.0% runtime.futex
       2   4.3%  89.1%        2   4.3% runtime.epollwait
       1   2.2%  91.3%        1   2.2% 0x000000000078341b
       1   2.2%  93.5%        2   4.3% github.com/dotcloud/docker.(*Container).Start
       1   2.2%  95.7%        4   8.7% net.(*conn).Read
       1   2.2%  97.8%        1   2.2% runtime.mallocgc
       1   2.2% 100.0%        1   2.2% runtime.memmove
```