Install doc wget and curl have develop branch instead of master

[jasonkastner]

I ended up having issues with the version 1.10.2 which is what develop branch was installing with the current URLs on the Installation page for WGET/CURL types of installation. To get 0.4.2, I had to change the URL to master.

curl -L -O https://raw.github.com/nvie/gitflow/**_master_**/contrib/gitflow-installer.sh
sudo bash gitflow-installer.sh