Set nvm proxy

1. On linux system nvm uses curl to download files if it exists, or wget. So we can configure proxy for them.

e.g. for curl, create a .curlrc file in home directory and input:

proxy = <host>:<port>

2. On Windows, even within cygwin, just export evironment variables as:

HTTP_PROXY="http://<hostip>:<port>"

HTTPS_PROXY="http://<hostip>:<port>" #This is most important

3. another method for Windows ( not tested )

run following command with administrator.

nvm proxy [URL]