Restructure all existing workshops to the new system

[moosichu]

• https://github.com/hackersatcambridge/workshop-example (change to point to workshop-template)
• https://github.com/hackersatcambridge/workshop-archlinux
• https://github.com/hackersatcambridge/workshop-continuous-integration
• https://github.com/hackersatcambridge/workshop-intro-to-git
• https://github.com/hackersatcambridge/workshop-intro-to-swift
• https://github.com/hackersatcambridge/workshop-emacs
• https://github.com/hackersatcambridge/workshop-open-source
• https://github.com/hackersatcambridge/workshop-python-ml
• https://github.com/hackersatcambridge/workshop-love2d
• https://github.com/hackersatcambridge/workshop-web-dev

Depends on #250