Renamed Lorentzian function to follow usual spelling

Not sure the usual spelling is correct but it's much more common.
Added guess methods

Designed to give initial estimates of the parameters for a given data
set
New Lorentzian function
Adjusted limit settings for overplots

Maintains current plot axes for an overplot, but adjusts the maximum
and minimum settings of the double spin boxes and sliders when the new
data is outside the limits.
Adding line plots

In 1D data, you can now right-click data and choose a line plot
directly, rather than plot points and then adjust them in the
Matplotlib settings.
Incorporating lmfit

Now uses Matt Newville's lmfit modules, wrapped to allow the definition
of multiple functions. This means that parameter limits have now been
enabled. Also, saving and reloading of fits should now work.