Add memcache to the dependencies

It looks like the Python memcache bindings are required to run zscore now, so
add that to the dependencies list.
Refactor the partial sleep into sleep.models

sleep.views had some moderately complicated logic for creating partial sleeps.
This moves that logic into sleep.models, in preparation for non-HTTP clients
that might want to create partial sleeps on behalf of users.
Add a more dev-targeted set of default settings
Add install directions
Zephyrbot to submit sleeps

This is basically a zephyrbot clone of the "Going To Sleep!" / "Waking Up!"
buttons (and mixing the two should work fine).
Merge pull request #30 from dehnert/zephyrbot

Ease the new-dev process and add a zephyrbot
Merge branch 'master' into metrics