Keep trace and profile files when go tool chain is not available

[zbindenren]

On our servers we have the go tool chain not installed and the servers are behind a firewall (no tunnels possible).

With this pull request it would be possible to perform a trace or pprof and copy the trace file to a system where I have the go tool chain installed. There I could run go tool trace <tracefile> and analyze the trace file with the browser.

This could maybe also solve #44.

If the go tool chain is not available you get the following output:

$ gops pprof-heap localhost:41081            
Profile dump saved to: /tmp/profile936731714     
                                    
$ gops pprof-cpu localhost:41081                                                                                                   
Profiling CPU now, will take 30 secs...   
Profile dump saved to: /tmp/profile262095472    
                                     
$ gops trace localhost:41081                                                                                                       
Tracing now, will take 5 secs...          
Trace dump saved to: /tmp/trace774199372  

[rakyll]

Thanks!