Fix improper current() handling in get_first() method due to PHP bug.
See http://bugs.php.net/bug.php?id=49369
Clean up the Collection class
The Collection class now implements ArrayAccess too
Merge branch 'master' of https://github.com/kijin/beaver

# By Kijin Sung
# Via Kijin Sung
* 'master' of https://github.com/kijin/beaver:
  The Collection class now implements ArrayAccess too
  Clean up the Collection class
  Fix improper current() handling in get_first() method due to PHP bug. See http://bugs.php.net/bug.php?id=49369