Until now a command must start with a keyword. This has been relaxed
and a command can now start with a keyword, a symbol, or a string.

This means that all of the following are legal ways to represent a
click:

[click] [:click] ["click"] (click) (:click) ("click")

#30

Using a wrong command name will now produce an error message
including the names of all currently implemented commands. This is
fetched dynamically by inspecting the MultiFn and should always be
up to date.

#30

The function to look up functions contained in a multimethod has been
moved to a utils namespace and now sports a proper docstring.