Optimise package installs in gastonjs

[nicksantamaria]

containers/gastonjs/1.0.2/Dockerfile

Line 8 in 6eae0fd

RUN apt-get update && \

Line 8: RUN apt-get update && \
Issue  Category      Title                 Description
    1  Optimization  apt-get update with   Use of apt-get update should be paired with rm -rf
                     matching cache rm     /var/lib/apt/lists/* in the same layer.
    2  Optimization  Consider              Consider using a `--no-install-recommends` when `apt-get`
                     `--no-install-recomm  installing packages.  This will result in a smaller image size.
                     ends`                 For
                                           more information, see [this blog
                                           post](http://blog.replicated.com/2016/02/05/refactoring-a-dockerfil
                                           e-for-image-size/)