Better delay times & error handling

• Delay values can be selectively omitted (the previous one will by used by default).
• Changed default delay time to 100ms.
• Fixed delay time units (from ms to 0.01s).
• API change: $->gifBinary() -> $->gif().
• Almost real error handling for image loading...
• Various other code improvements (errors, control flow, cleanup etc.)
• Some cleanup & refresing of the docs. (incl. comments)