Color-coordinate the loud modal indicator

Green when in Edit mode
Gray when in Command mode

closes #24, thanks to @BernhardKonrad for the idea
also make the pencil green, while we're at it!
updated README
Two lines for Command Mode to fix #28
Update custom.js

Remove the "Mode" in "Command Mode" to shorten the text for smaller Laptop screens.
Merge pull request #42 from BernhardKonrad/mode-colors

Two lines for Command Mode to fix #28
Merge pull request #41 from ivanov/mode-colors

color-coordinate the edit/command mode indicators