Added the basis of rules.

Added the implementation of rules.

When the client is to be spawned on a different workspace (without follow set to true) the client is expanded to be the full size of the display (larger than fullscreen) and appears behind all workspaces.
Prevented visual bugs and segfaults when a client was sent to a new workspace without focus following it.
Added a warning about updating focus of clients on other workspaces.
Fixed a missing comma.
Update README.md

Added description of rules.
Added docs for apply_rules.
Merge pull request #30 from HarveyHunt/feature/rules

Feature/rules