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/zulu/Dockerfile

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

docker/zulu/install.zsh

@@ -0,0 +1,10 @@
+#!zsh
+
+# install zulu https://github.com/zulu-zsh/zulu
+curl -L https://git.io/zulu-install | zsh && zsh
+
+{
+echo 'zulu fpath add ~/p9k'
+echo 'zulu fpath add ~/p9k/functions'
+echo 'zulu theme powerlevel9k'
+} >> ~/.zshrc