Handle digest values of string or buffer

In nodejs 0.8.x, hash.digest() returns a string. In 0.10.x, it returns
a Buffer.

output.write() was throwing a type error when a buffer was provided.
I've put in some switcheroo code that checks the type of the digest
and uses the correct buffer-writing code.
Remove older comment
Use full syntax for setImmediate()
Add image.url to list of expected indices
More forgiving handling of unknown targets in activities
Better notice for login web ui test
Command-line script to post a file
Add another endpoint for plugins
Group inbox gets all finishers
Merge branch 'master' of github.com:e14n/pump.io