Added sticky table headers to history page

The data on the history page is a pretty long list. I thought it might
look at bit nicer to have a sticky table header so that further down the
list you still have an idea of what you're looking at!
Fixed numeric sorting issue on history page

Numeric columns on history page were not sorting properly because their
sType was numeric instead of num-html. Thought this was a problem with
my stick headers, turned out not to be, so I fixed it anyways. Also,
table header now has pointer to show that header is interactive.
Merge pull request #26 from kand/sticky-table-headers

Added sticky table headers to history page, fixed history data sorting issue