anchor.diff:  
   # Install dependencies for Ruby
   # Also installs dependencies for the following common gems:
  -# 
  +#
   # gems      dependencies
   # ------------------------------------------------------------------
   # curb      libcurl3, libcurl3-gnutls, libcurl4-openssl-dev
   # pg        libpq-dev
   # rmagick   libmagickwand-dev
  -# nokogiri  libxml2-dev
  +# nokogiri  libxml2-dev, libxslt-dev
   # sqlite3   libsqlite3-dev
   # mysql2    libmysqlclient-dev
   
  
positive.code:         libyaml-dev \
          libz-dev \
          libxml2-dev \
          libsqlite3-dev \
          libmysqlclient-dev \
          libpq-dev \
  
negative.code: 
  # Preinstall ruby runtimes.
  # The LAST version in the list is set as the default.
  ENV PREINSTALLED_RUBY_VERSIONS 2.0.0-p648 2.1.8 2.2.3 2.2.4
  RUN for V in $PREINSTALLED_RUBY_VERSIONS; do \
      rbenv install $V; \
      rbenv rehash; \
  