Fix critical error in XMLHTTPRequest send()

There is critical Exception (NS_ERROR_XPC_NOT_ENOUGH_ARGS) in old versions of Firefox (v. 2.0 was checked). Also there could be the same problems in other old browsers
Polyfill doesn't work in all browsers except IE

In all browsers except IE script doesn't work because of IE versions detection. Variable "ie" is undefined for other browsers and incorrect onreadystatechange initialization is using.
Fix in removeMediaQueries function

removeMediaQueries() functions works incorrect - it removes only first media block
Fix in rem to pixels conversion

parseInt() function trims all float values and Math.round() function doesn't have any sense. There should be parseFloat() function
Fix in original font size calculation

There are two bugs in font size calculation:

1) If font-size style was changed for body element - "rem font size" will take changed value but Root Em value should be used. For example:

body {
  font-size: 0.75em;
}

in this case all modern browsers will render rem with 16px, but script will use 12px.

2) Font size calculation doesn't work when font size is in em or pt. Raw em/pt values are using which is completely incorrect
IE detection code was refactored

http://tanalin.com/en/articles/ie-version-js/

Internet Explorer browser of versions 10 and older can be detected in JavaScript by checking existence of the nonstandard document.all object available only in IE10 and older. 

Such objects for versions of IE up to 10 inclusive are listed in the following table. 
IE ver	Supported standard object
 10+	window.atob
 9+	document.addEventListener
 8+	document.querySelector
 7+	window.XMLHttpRequest
 6+	document.compatMode
Variable name for IE code detection was changed
Changes in original fontSize calculating

1) Temporary elements did not remove correctly
2) Code was changed to match JavaScript Style Guide (https://github.com/natgeo/javascript)
3) Optimization for js minimization

Notice: today I found that Respond.js plugin has similar font-size detection. But I found that all browsers calculate rem according to html element font-size. That mean that in case when font-size was changed by css or style attribute calculated font-size should take into consideration this value. Respond.js also resets this value like a body font-size. But this behavior doesn't match to browsers behavior (at least IE and FF works in this way)
Actual version compiled with Google Closure Compiler

Actual version compiled with Google Closure Compiler (http://closure-compiler.appspot.com/home).
Optimization: Whitespace only
Actual version compiled with Google Closure Compiler 

Actual version compiled with Google Closure Compiler (http://closure-compiler.appspot.com/home).
Optimization: Simple
Actual version compiled with Google Closure Compiler 

Reverted to non-optimized version. There is a bug with "simple" optimized version - code after compilation is broken
Merge pull request #48 from alray/master

Several crittical bugfixes and improvements. Better IE version detection and base font calc.