Allow users without any feeds to view feed-specific pages.

Fixes #84.
Clean up handleRoot.

Split the big, individual-feed case into its own function. Also use
smaller local variable names.
Use the more-go-idiomatic switch instead of if/else if/else.
Rename /list to /manage.

It's a more accurate and descriptive name.
Make all header linkes more acme-like.

Fixes #129
Merge pull request #131 from eaburns/dev/eaburns

Some smaller changes.