Improve readme file

Thank you for making this template. However, some issues when trying out this:

The git command did not work at first, the clone should go before --depth argument.
The bin/setup, bin/server and bin/middleman needed special permissions, had to use chmod +x

Would appreciate more detail instructions.

Start by reading the README and checking the documented git clone command plus the bin/setup, bin/server, and bin/middleman scripts. Verify the setup steps and executable-permission requirements, then update the README so a fresh user can follow the instructions successfully.

Written by the indexing model from the issue text.