#271 add proxy with auth,

this is workaround for #271. but this code has not been tested, since i do not have test environment and our client who had this trouble somehow resolved this problem before I create this patch. I just create PR not to forget code.

if you find someone with proxy/auth trouble , please check if
https://gist.githubusercontent.com/k-okada/cf79038d1cffc943a8d3/raw/b4d21725af7de2ac318d5a27ca6003bb1e6e0d95/rosdep work

this workaround is based on http://stackoverflow.com/questions/34079/how-to-specify-an-authenticated-proxy-for-a-python-http-connection

This patch breaks the Python 3 package. @k-okada Please add unit test coverage for the new code.