Add support for `dojoup update`

[kronosapiens]

Is your feature request related to a problem? Please describe.
Currently, running dojoup does not update Dojo to the latest version.

Describe the solution you'd like
Add a dojoup update option which updates all Dojo components

Describe alternatives you've considered
I had to update Katana to 1.5.2, which involved:

• rm -rf ~/.dojo
• Re-running the dojoup installer
• Updating my ~/.zshrc file to source the env
• Running dojoup

Once I have installed dojoup once, I should be able to update to the latest Dojo version.

[ritik4ever]

please review my PR @kronosapiens