Fix floating window initial sizes

When I added support for propose dimensions, I was foolishly just
choosing the min (or max) if only one was set. However, a lot of windows
will a set a very small min size with no max, which meant we would have
really tiny windows when first floating one. The fix was to try set to
75% but then clamp to the min/max dimensions the window gave.

After fixing that, there was still an issue where windows kept their
size after being floated. That's because there was a propose_dimensions
call happening later in Window.manage(). I'm skipping that now if a
window became floating in the same manage event.

docs/TODO.md

@@ -31,3 +31,4 @@ These are in rough order of my priority, though no promises I do them in this or
 - [x] Add options to the bar
 - [x] Make a Rect struct to combine x, y, width, and height
 - [x] Support window rules (float/tags by app-id/title)
+- [x] Fix resizing size when you pop a window out, basically, it start with its current size but then when you try resize it goes to 75%