Update Dockerfile

Dockerfile

@@ -4,7 +4,7 @@ MAINTAINER Florian Thöni <florian.thoni@floth.fr>
 ENV DEBIAN_FRONTEND noninteractive
 
 RUN apt-get update; \
-   apt-get install -y build-essentials \
+   apt-get install -y build-essential && \
    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 RUN curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.6/install.sh | bash