Jupyterthemes

- merged [PR 227](https://github.com/dunovank/jupyter-themes/pull/227) submitted by [rightx2](https://github.com/rightx2) fixing encoding error

- merged [PR 215](https://github.com/dunovank/jupyter-themes/pull/215) submitted by [PegasusWithoutWings](https://github.com/PegasusWithoutWings) fixing lesscpy dependency
- updated setup.py dependencies to fix Travis checks

- fixed soft-selected cell border style
- misc. style updates

- updated all styles (fixed broken themes)
- misc. style updates

- merged [PR 180](https://github.com/dunovank/jupyter-themes/pull/180) submitted by [fry95116](https://github.com/fry95116) fixing str formatting issue with `-mathfs` arg
- misc. style updates

- fixed soft-selected cell highlighting
- misc. style updates from "safarinb" project (buttons, tabs, hover, focus, etc.)