change typeof <v> !== 'undefined' to <v> !== void 0

[mikrofusion]

This request is to modify the places in the code where "typeof !== 'undefined'" to " !== void 0" where is a variable (in this case exports and window).

A few reasons for the request:

1. I have seen performance improvements by going with the void 0 approach. Supporting data: http://jsperf.com/typeof-vs-undefined-check/15
2. It reduces the overall number of characters used to test whether the variable is undefined (an overall bandwidth improvement).
3. Although 1 & 2 are negligible for this project due to only being used in a few places, this seems to be a best practice being used by other libraries (i.e. underscore.js) and would be good to use for continuity of best practices between projects.

Thanks!

[braddunbar]

Hi @mikegroseclose! While Backbone and Underscore do use void 0 in place of undefined as a matter of style, this code is comparing the type to 'undefined' (note the quotes) in order to avoid throwing when it's not in scope.