Added checkboxes in options to enable/disable things instead of selecting 0 to disable
Cleaned code up to store 0 instead of using a separate variable to disable - retains compatibility with previous settings
Modified colourisation to ignore asianness < 0
fix options checkbox bugs

reset background updating interval dynamically
fix bug that made HAC_HTML.colorize depend on asianness_on being set to
true
slide in/out instead of fade in/out options DOM
set default nonzero spinbox values if colourisation or refresh is
disabled
Merge pull request #15 from xsznix/options_checkboxes

Options checkboxes: adds checkboxes to intuitively enable/disable grade colourisation and background updating