changed how shell script could be sourced in katas

[schiluveri]

All README.md files from the suggested list* have been updated to use source command instead of ..

• https://github.com/praqma-training/git-katas/blob/master/Overview.md

[schiluveri]

Looks good to me. Is there a specific reason why you only changed the ones in the overview, not the remaining handful?

Apparently, all setup instructions that stated to use . were replaced with source. If you find any other instance, let me know ;)

[schiluveri]

Re-opening (closed this PR unintentionally.)