Various UI tweaks.
Merge branch 'master' of github.com:kentonv/sandstorm

Conflicts:
	website/apps/index.html
Add missing image file.
Web site tweaks.
Show a big green arrow pointing at 'My Files' after successful app installation.
More web site tweaks.
Add some info about debugging to the readme.  Also disallow passing bad package IDs to /install as a precaution.
More web site tweaks.
Today's changes.  Sorry, not organized.
Document dependency on XZ
Merge pull request #8 from abliss/docpr

Document dependency on XZ
Web site updates.
Add extended documentation about setting up the shell, inculding port forwarding issues and an example nginx config.  Fixes #2.  Fixes #7.
tweak
Comment on mongoDB size issues.
Bold, not italic.
More clarifications.
Implement ability to send invite e-mails from web interface.
Make e-mail invites more robust.
Improve keepalive handling, which has been producing lots of errors of late.