Make content scrollable where needed. Fixes #24. Fixes #25.
Tweak notes about public domain code taken from libb64.
Tweak notes about code copied from Meteor, and expand dependency list on about page.
Style tweaks.
Change e-mail dates to nanoseconds instead of microseconds, for conformity with other Cap'n Proto protocols.
Merge branch 'master' of github.com:kentonv/sandstorm
Add getUserAddress to HackSessionContext
Remove getAddress function (superceeded by getPublicId for now)
Always make the grain's address be the `from` in the smtp envelope.

Also remove old logic for replacing `from` header in messages, and
instead allow either the grain's address or the user's sandstorm
registered address to be used.