Fixed support for IE8 and IE9

Fixed support for IE8 and IE9 using mediaQueryPolyfill, and setting
mediaQueriesSupported
Fixed format of README
README Microfix
Code refactoring + added function comments in code + IE7 won't break
Updated browser support section in README
README microfix
Fixed a bug when srcset was string and no standard picture
Moved test files in test folder
A note about Internet Explorer
Changed note about IE
Changed usage code
Edited note about IE desktop browsers
Edited note about IE
Edited note about IE
Added a demo with server side scaled images (pixtulate)
Merge branch 'master' into gh-pages