Update docs with curl cmdline which follows redirects.

To improve security github has moved all user content from the github.com domain to githubuserconent.com domain, see https://developer.github.com/changes/2014-04-25-user-content-security/ for more information.

They offer redirects from the original locations, but curl **won't** follow redirects by default. Annoying `curl` doesn't error even give you an error when it hits a redirect and does nothing! Thus the command 
`curl https://raw.github.com/robmadole/jig-plugins/lists/common.txt > .jigplugins.txt` looks like it succeeds but just ends up creating an empty .jigplugins.txt file. This confused me for a while.