Refactor readme with step-by-step instructions
minor tweaks, formatting fix
Add troubleshooting section
Prefer 'require' over 'use'
use own image => use vmfest-image; simplify instructions; link to vmfest project
Add Next Steps section
Add link to group-spec reference documentation
Clean up Step 3-B, download existing vmfest virtualbox image
explain pallet.configure/compute-service as alternative to instantiate-provider
Merge pull request #12 from alanning/patch-1

Refactor readme with step-by-step instructions