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/zplug/Dockerfile

@@ -0,0 +1,7 @@
+FROM p9k:base
+
+COPY docker/zplug/install.zsh /tmp/
+RUN zsh /tmp/install.zsh
+
+COPY ./ p9k/
+COPY docker/zplug/zshrc .zshrc

docker/zplug/install.zsh

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+#!zsh
+
+curl -sL --proto-redir -all,https https://raw.githubusercontent.com/zplug/installer/master/installer.zsh| zsh
+
+# git clone https://github.com/zplug/zplug "${HOME}/.zplug"

docker/zplug/zshrc

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+#!zsh
+
+source ~/.zplug/init.zsh
+zplug "${HOME}/p9k", use:"powerlevel9k.zsh-theme", from:local, as:theme
+zplug load --verbose