Update extra.sh

Pip Install failed due to an old or outdated link 

Old:  https://raw.github.com/pypa/pip/1.4.1/contrib/get-pip.py
New:  https://raw.githubusercontent.com/pypa/pip/1.4.1/contrib/get-pip.py
Merge pull request #370 from mikehumphrey/patch-1

Update extra.sh  Issue: #369