A small correction to READM instructions

[andreasilvau]

Hi everyone,
Thank you for the nice work you put on in here.

I had a small issue forking this theme. I followed the instructions under "Github Pages installation" and modified the repository name to "andrasilvau.github.io". But the page was not building. It turned out that the only available git branch was 'gh-pages' but Github was expecting the repo to have a "master". I had to run this command to solve the problem
git checkout -b master
And then push those changes using
git push --set-upstream origin master

That solve the problem for me
Thanks!