Remove dependency on EventEmitter2; it wasn't being used internally. This may break something externally.

Please let me know if this commit has broken your system. If it
has, that means that you were using the EE2 functionality, probably
in the join/send stuff.
Modify default weight function

The previous default weight function was Math.random(). Now, I have exposed
`Discover.weight` as an over-ridable function for setting the default weight.

The default implementation of Discover.weight is the negative value of
`Date.now()` divided by 10 to the power of the number of digits in the
value of `Date.now`. This method will favor the earliest started nodes to be
master nodes while keeping the automatically generated weights > -1 and < 1.
Merge branch 'master' of github.com:wankdanker/node-discover