Commented the Dockerfile and removed "apt-get update" command -> smaller image

Dockerfile

@@ -1,6 +1,18 @@
+# A simple Dockerfile for building Kvazaar from the git repository
+# Example build command when in this directory: docker build -t kvazaar .
+
+# Use Ubuntu 15.10 as a base for now, it's around 136MB
 FROM ubuntu:15.10
+
+    # List of needed packages to be able to build kvazaar with autotools
     ENV REQUIRED_PACKAGES automake autoconf libtool m4 build-essential git yasm
-    RUN apt-get update
+    
+    # Running update causes extra data to be stored in the image
+    # We don't need to update right now.
+    #RUN apt-get update
+    
+    # Run all the commands in one RUN so we don't have any extra history
+    # data in the image.
     RUN apt-get install -y $REQUIRED_PACKAGES ; \
     git clone --depth=1 git://github.com/ultravideo/kvazaar.git; \
         cd kvazaar; \
@@ -12,6 +24,7 @@ FROM ubuntu:15.10
         apt-get autoremove -y; \
         apt-get clean all; \
         rm -rf /var/lib/apt/lists/*
+    # Because we build only the static binary, copy that to the root
     COPY src/kvazaar /
 ENTRYPOINT ["/kvazaar"]
 CMD ["--help"]