Names that reflect their non-generality.

We do not just expect any "data" here, we specifically expect a table of
commits data frame.
Added TODO: consider replacing ggplot2 with lattice.

For performance reasons.
Plot distribution of edit sizes per commit.
Re-organized a bit.
Fixed names to match the data.
Better fit within 79 characters.
Removed redundancy and added better fit.
Don't forget to actually use the filtered table.
Plot both, histogram and KDE.
Compacted aesthetic layer assignments.
Updated example with filenames of new plots.
Updated execution time.