Add --path flag

[nickwarters]

Adds a --path flag following suggestion in comments of #58

• use . for current directory
• use relative path to current directory e.g. ./test-folder
• paths without /, \ or . prefix will be treated as relative to current directory
• use absolute paths e.g. /users/{username}/dev
• ~ is expanded to $HOME env variable so ~/dev and /Users/{username}/dev are equivalent if $HOME is set to /Users/{username}

[nickwarters]

@Melkeydev what are your thoughts on this feature? Worthwhile or not? If not, let's close off and knock another one off the queue :)

If you do think it's a good idea I'll rebase and get the the linting sorted