JQuery removal, some error checking & minor css changes

 * Replaced jquery calls with javascript calls
 * Moved script tag to the bottom to reduce time till 1st draw
 * Replaced divs containing calculated values with spans
 * Removed float property from .planet divs
 * Simple input sanitization via RegExp
 * Added 'kg' text on .planet span:after pseudo element
small fixes

 * Removed some js global variables
 * added missing vendor prefixes for border-radius
 * Added missing initial value in the Greek translated page
Autofocus on input element
Merge pull request #1 from hardalias/jquery_free

πάει ο Τζέη Κιου Έρης