Added label option shorten_by_padding. This is an option that will shorten text based on padding_x. Also added a funtion to trim spaces off of lines. This aligns text when it is split by size constraints.
* fix `make clean` to remove cythoned .c files
* update _scroll_x_mouse and _scroll_y_mouse to fix scrollview jumping
* merge upstream
* merge upstream
Work around for to use the old implementation of Screen.
Allow use of custom pre 1.6.0 style Screen classes.
Merge branch 'screen-fix'