Add favicon.ico to vprof

[nvdv]

Currently vprof does not have favicon and server throws IOError:

Exception happened during processing of request from ('127.0.0.1', 52771)
Traceback (most recent call last):
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/SocketServer.py", line 599, in process_request_thread
    self.finish_request(request, client_address)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/SocketServer.py", line 334, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "vprof/stats_server.py", line 37, in __init__
    self, *args, **kwargs)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/SocketServer.py", line 655, in __init__
    self.handle()
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/BaseHTTPServer.py", line 340, in handle
    self.handle_one_request()
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/BaseHTTPServer.py", line 328, in handle_one_request
    method()
  File "vprof/stats_server.py", line 52, in do_GET
    with open(res_filename) as res_file:
IOError: [Errno 2] No such file or directory: 'vprof/frontend/favicon.ico'

Add favicon.ico to vprof to fix this.