Update README.md

Add VirtualBox to prerequisites
Merge pull request #20 from adamlofting/patch-1

let's be fair - yes.
let's do some AWS work
refine
aws-env rewriting script
spacing
varname change
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Fix Bug 968947 - Use --depth option when cloning repositories
force reset when reset is used
Merge branch 'master' of github.com:mozilla/webmaker-suite
python vs python2 for htmlsanitizer
renamed the add-remote script to add-contributor-remotes, because that's what it does
new repo scripts
no git@github
empty commands means [], not false
made ES clearing a runtime flag
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