Use chroma syntax highlighting and dev changes

- Use Chroma for syntax highlighting instead of Pygments which removes
  the need to manage a python install and Chroma is faster.
- Add the ability to optionally pass a working dir to main. This
  allows cycle to build sites from within the REPL.

Bump python version in CI

This builds pygments in CI to enable syntax highlighting.

Pygments has to be available when the image is created _and_ on the
host system where the executable is run. This seems obvious in
hindsight but I missed it.

Enable pygments syntax highlighting.

Fixes RSS date generation to be valid RFC-822[1]

[1]: https://tools.ietf.org/html/rfc822#section-5.1

Fixes CI and a few changes.

Travis should know be able to build executable that work. I decided to
build SBCL from source in CI to pull in a newer version of asdf.

I removed the standalone package files since packages and files have
no direct relationship in CL.

I removed the `ecl` make task and README mention since I never use it.

Proper date formatting is here!

Posts on the index and post pages now use the format `January, 10, 2019`.

RFC-822 date generation has been massively cleaned up as well.

generate now produces proper slugs

fix RSS timezones

linked post support for RSS