Presently when you `^C` in `zola serve` it is painted with the same
color as the previous message. This PR always ensures to reset the color
in colorize, before writing the newline.

Closes #726

To also process the ones found in templates

Closes #669

Closes #607

Closes #576

- unless forced, only use colors in tty
- support CLICOLOR and NO_COLOR vars
- switch to termcolor crate to handle output coloring

Fix #72

Fix #66