Height calculation off by one error with header

[sachabest]

There appears to be an error in total wrapper height calculation when there is a table header included. In the case where you have a search field on a table wrapped with angular virtual scroll, the last row will be hidden as the height calculation doesn't take into account the header. A patch fix is to simply add +1 to newValue.len in https://github.com/stackfull/angular-virtual-scroll/blob/master/src/virtual-repeat.js line 355, but a more robust solution would be to add a parameter to the directive allowing the user to specify the thead element and/or height.