Improve installation instructions on README
Improve installation instructions on README

Change directory to allow `heroku create` automatically add a `heroku`
git remote.
Comment in a command run by Zsh is interpreted as part of the code,
giving a `Invalid arguments` error.

mpraglowski/stringer,InPermutation/stringer,lodestone/stringer,adscott/stringer,dperson/stringer,geemus/stringer,jqr/stringer,milligramme/stringer,dperson/stringer,jeroenj/stringer,nibble/stringer,swanson/stringer,Koronen/stringer,dperson/stringer,nibble/stringer,Koronen/stringer,bkbabydp/stringer,wwwjfy/stringer,nibble/stringer,milandobrota/stringer,jeroenj/stringer,milligramme/stringer,adscott/stringer,milandobrota/stringer,adscott/stringer,geemus/stringer,geemus/stringer,swanson/stringer,bkbabydp/stringer,adscott/stringer,thiagosil/stringer,Koronen/stringer,swanson/stringer,jqr/stringer,nibble/stringer,swanson/stringer,dandorman/stringer,jqr/stringer,run-project/stringer,mpraglowski/stringer,jeroenj/stringer,thiagosil/stringer,thiagosil/stringer,jqr/stringer,dandorman/stringer,nobuti/stringer,run-project/stringer,Koronen/stringer,milandobrota/stringer,lodestone/stringer,nobuti/stringer,mpraglowski/stringer,jeroenj/stringer,InPermutation/stringer,nobuti/stringer,InPermutation/stringer,wwwjfy/stringer,milligramme/stringer,dandorman/stringer,dperson/stringer,lodestone/stringer,geemus/stringer,run-project/stringer