test-in-docker: quickly test frameworks in docker

This adds `./test-in-docker` for quickly playing with various frameworks.

All the containers are based off Ubuntu 14.04 which has ZSH 5.0.2.

Thanks to @dritter for figuring out all the framework installation
methods.

docker/prezto/Dockerfile

@@ -0,0 +1,6 @@
+FROM p9k:base
+
+COPY docker/prezto/install.zsh /tmp/
+RUN zsh /tmp/install.zsh
+
+COPY ./ p9k/

docker/prezto/install.zsh

@@ -0,0 +1,18 @@
+#!/bin/zsh
+
+set -eu
+
+git clone --recursive https://github.com/sorin-ionescu/prezto.git "${ZDOTDIR:-$HOME}/.zprezto"
+
+setopt EXTENDED_GLOB
+for rcfile in "${ZDOTDIR:-$HOME}"/.zprezto/runcoms/^README.md(.N); do
+  ln -nsf "$rcfile" "${ZDOTDIR:-$HOME}/.${rcfile:t}"
+done
+
+ln -s "${HOME}/p9k/powerlevel9k.zsh-theme" \
+  "${HOME}/.zprezto/modules/prompt/functions/prompt_powerlevel9k_setup"
+
+echo "zstyle ':prezto:module:prompt' theme 'powerlevel9k'" \
+  >> "${HOME}/.zpreztorc"
+
+# EOF