Update README.md to include working install instructions

I've updated the "Creating Your Own Aphostrophe Project: The Easy Way" paragraph to be more clear and mainly to update the `git clone` url (using the ssh endpoint results in a `Permission denied (publickey)` error, the `https` version should be used instead.

I've also updated the suggested way to update the remote `origin` as it should be done with git tools instead of editing the `.git/config` file by hand.