Adding function to toggle bg color.

This is the function and associated CSS only. The button has not yet
been added.
Moving characters to separate tab.
Using terminus for preview font.
Adding dynamic elements with return code.

Code generation can now output functions to insert dynamic elements into
the prompt. Currently the only element in this category is the return
code, which will print whenever the previous command exits with nonzero.
Fixing color code output that was broken by the last commit.
Moving spectrums under elements list.
Adding titles to some elements to prep for tooltips.
Adding doctype.
Now executing tabs() on document ready without wrapper function.
Adding more tooltip titles.
Attaching tooltips to available options.
Fixing code output box that was broken by adding doctype.
Merge branch 'master' into gh-pages