fix an error of varible declaration  and an error in older versions of IE

Error of varible declaration : 
There is a variable declared but never used in function mq.listenForChange.
I think is maybe a error, I change variable name to query_string.

Error in older versions of IE
MQ.removeQuery threw a null error in older version of IE because old IE not support Array.properties.indexOf. more info here: http://kangax.github.io/es5-compat-table/#Array.prototype.indexOf . the fix does'nt seem to throw a new error in other browsers.