APP_NAME and APP_VSN calculation needs to run in the right directory

[mahcloud]

Summary of changes

TL;DR docs example wasn't in the right directory

I wanted to use the grep script (below) in your docs because well it looked great!
When I ran it, it was getting me the output:

grep: mix.exs: No such file or directory
grep: mix.exs: No such file or directory

The script in your docs that I'm referring to:

APP_NAME="$(grep 'app:' mix.exs | sed -e 's/\[//g' -e 's/ //g' -e 's/app://' -e 's/[:,]//g')"
APP_VSN="$(grep 'version:' mix.exs | cut -d '"' -f2)"

Checklist

• New functions have typespecs, changed functions were updated
• Same for documentation, including moduledocs
• Tests were added or updated to cover changes
• Commits were squashed into a single coherent commit

Licensing/Copyright

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[bitwalker]

Thanks!