Removed var duplication, cached cookies.length

Always good to save a couple of bytes where possible, multiple vars may not be stripped during minify so lets do it now

Calculate length before the forLoop is initiated, can be faster in extreme cases or when you need max performance - see http://jsperf.com/angular-foreach-vs-native-for-loop/29
More duplication removed and compared size

Removed duplication of checking if expires is number, adding within cookie creation

Also compared file size with previous changes - when uglified and gzipped, its smaller by 4 :)

  raw     gz Sizes
 1298    698 jquery.cookie-old.js (v1.4.1)
 1255    694 jquery.cookie.js (proposed changes)
Oops, breaking changes, fixed

Optimisations still smaller, reverted some changes as they broken tests and are required to check if expires is a date - not just a number!

   raw     gz Sizes
  1298    698 jquery.cookie-old.js (v1.4.1)
  1297    697 jquery.cookie.js (proposed)
Removed whitespace, saved more bytes in gzip

Fixed minor issues with whitespace based on @Krinkle notes

Also saved more bytes when gzipped, it is now 696 bytes - a 2 byte saving! :)

   raw     gz Sizes
  1298    698 jquery.cookie-old.js
  1295    696 jquery.cookie.js