Merge pull request #51 from stekycz/stekycz

Button selector should also select tag <button>
Cancel in 'beforeSend' is checked by .status [closes #48]
Fixed binding of form buttons [closes #52]
Added extension for auto-removal of ?_fid [closes #42]
Added method '$.fn.netteAjaxOff()'
Global 'window' variable made local
Merge pull request #54 from uestla/patch-1

Global 'window' variable made local
Event 'prepare' gets disabled with whole ext
Merge branch 'master' of github.com:vojtech-dobes/nette.ajax.js