Rework how highlighting works.

Makefile

muppet/__main__.py

muppet/format.py

muppet/output.py

muppet/syntax_highlight/__init__.py

muppet/syntax_highlight/andre_simon.py

muppet/syntax_highlight/plain.py

muppet/syntax_highlight/pygments.py

static-src/.gitignore

static-src/Makefile

static-src/README.rst

static-src/_breadcrumb.scss

static-src/_breadcrumb.scss.map

static-src/_highlight.scss

static-src/build_css.py

static-src/colorscheme/default.yaml

static-src/highlight/andre_simon.yaml

static-src/highlight/muppet.yaml

static-src/highlight/pygments.yaml

static-src/style.scss