Make command log colorful

[bmag]

Add two faces - one for keys and one for commands.
You might want to adjust the faces' default values. They work fine with the theme I'm using, but not with the default emacs theme.

Implements #7

[stardiviner]

+1 good job

[bmag]

@lewang did you see this?

[emacs18]

@bmag Could you resolve the conflict so that your change can be checked into this git repo so that spacemacs can use this repo instead of your custom repo?

I took a shot and tried to resolve the conflict as shown below.
The conflict is just in one line.

                 (insert (propertize (format "%s" (if (byte-code-function-p cmd) "<bytecode>" cmd))
                                     'face 'command-log-command))

[bmag]

@emacs18 your resolution looks correct to me. Is there anyone that will merge this PR if I resolve the conflict?