Add a Makefile that creates API documentation and runs unit tests
README: Make it clear that the API is not yet stable
Rename usesAction() to callsAction()

We invoke actions like functions and so it is more accurate to ask
whether or not an event ‘calls’ an action than asking if an event
‘uses’ an action.
Do not allow changes to the metatable of events

This patch eliminates a source of potential bugs: external
manipulation of the metatable for events.  We include a new unit test
to ensure that Luvent raises an error if we attempt to change an
event’s metatable.
Make sure addAction() accepts tables with a call() metamethod

We allow addAction() to accept a table in place of a function as long
as that table defines the call() metamethod.  This patch adds an
explicit test for that functionality.
Improve the test regarding the required argument of addAction()

The addAction() method requires either a function or a table that has
an implementation of the call() metamethod.  This patch improves the
unit test for the arguments of addAction() by calling it with a table
that does not have that metamethod.  In this situation the method
should always result in an error, which is what the test expects.
Improve documentation for Luvent properties and methods