Use 'w steps' for file count.

Instead of 'w histeps', we use 'w steps', which doesn't make the last commit
seem like it removed all the files.

gitstats

 set ylabel "Files"
 set xtics rotate by 90
 set bmargin 6
-plot 'files_by_date.dat' using 1:2 w histeps
+plot 'files_by_date.dat' using 1:2 w steps
 """)
 		f.close()