update workflow tutorial - ssh keys for master pull

Added a note regarding the need for SSH keys to be registered with github in order to use the given pull command, and the option to use https instead.
update 'before you code' - ssh keys for master pull

added note about the need for having ssh keys registered with github to run the given command, and about the option of using https instead.
Merge pull request #156 from aryehpro/patch-1

update workflow tutorial - ssh keys for master pull
Merge pull request #157 from aryehpro/master

update 'before you code' - ssh keys for master pull
repaired an unclear instruction