Add vader tests and docker setup

Dockerfile

@@ -0,0 +1,17 @@
+FROM tweekmonster/vim-testbed:latest
+
+ENV PACKAGES="\
+    bash \
+    git \
+    python \
+    py-pip \
+"
+RUN apk --update add $PACKAGES && \
+    rm -rf /var/cache/apk/* /tmp/* /var/tmp/*
+
+RUN pip install vim-vint
+RUN git clone https://github.com/junegunn/vader.vim vader
+
+RUN install_vim -tag v7.4.1099 -build \
+                -tag v8.0.0027 -build \
+                -tag v8.1.0519 -build