Update version number.

Update version number to 3.7

Merge pull request joostkremers#37 from sixshotx/patch-1

Update writeroom-mode.el

Update version number.

Update version number to 3.5

Update version number.

Update version number.

Change version number to 3.2

Keep track of frame to which changes are applied.

Make global effects functions compatible with minor mode functions.

Global effect functions should now activate the effect if they receive 1
as argument and deactivate them if they receive -1. This way, it is
possible to add a global minor mode to `writeroom-global-effects`
without having to write a custom function.

This implements the suggestion in joostkremers#21. It also creates an
incompatibility with existing configs, so the major version number is
being bumped.