Added resizeDelay options and fitrows gutter width and height

Case :
1. Dealing with CSS3 animation or Custom javascript that will effect the child element height, isotope firing the layout too early causing the layout to be on top of each other or at least part of the child is on top of each other.
2. When dealing with isotope + bootstrap, fitRows cannot have gutter width as it will break bootstrap grid columns but we do need the height gutter.

Solution :
1. add a delay options to allow user to define how many ms should isotope to wait before layouting on resize events, this would be great if it can be also used to delay the initial initialization.
2. added options to define gutter width and height separately.