Allow any var that sourced from a require in disallowMultipleVarDecl

[ValYouW]

Hi,

In disallowMultipleVarDecl, when using allExcept require, what do you think about allowing all vars that sourced from a require call?
For example, this is currently failing on the Emitter var

var fs = require('fs'),
    Emitter = require('events').EventEmitter;

How about allowing such cases?
I played a little bit with the rule and came up with this:
ValYouW@999c714

Not sure it's 100% ok as I am not so familiar with esprima...

[markelog]

I think that would be a good idea, i think current behaviour could be considered as bug

[hzoo]

@ValYouW maybe paste some code and play around with http://astexplorer.net/ if you want to make a PR for it later

[ValYouW]

Ahh, sorry for all the commits mess...
Created a PR #1849 (with tests) lets discuss it there...