Extract default theme from picocms/Pico repo

This repo is a copy of the picocms/Pico repo (https://github.com/picocms/Pico) at commit 82a342ba445122182b898a2c1800f03c8d16f18c with rewritten history. Only commits which are relevant for the themes/default/ directory (https://github.com/picocms/Pico/tree/82a342ba445122182b898a2c1800f03c8d16f18c/themes/default/) were preserved. The command used to create this repo can be found at http://stackoverflow.com/a/37037151.

Pico is licensed under the MIT License (https://github.com/picocms/Pico/blob/82a342ba445122182b898a2c1800f03c8d16f18c/LICENSE.md).