0.3.1

performance improvements:
- added queue functionality to prevent browser from micro-freezes
- loop items with 'for' instead of 'jQuery.each()', because its mutch faster
- switched from jQuery's 'element.offset()' to nativ 'element.getBoundingClientRect()'
- use late-binding of events and function queues to get best performance
- calculation will only be queued and executed once at a time
- use short-hand whenever its possible

other changes:
- bind error event before first images gets loaded
- some better variable declarations
- throttle is now enabled by default
- 'visibleOnly' is now disabled by default
- name of the handle identifying attribute is now changeable in configuration
- rename variables to leading underscore for better internal identification
- change descriptions to valid jsdoc for variables and functions in development file
- enabling strict mode on whole library
- fixed typos