Update Readme, add gitpod support

.gitpod.Dockerfile

@@ -0,0 +1,14 @@
+FROM gitpod/workspace-full
+
+USER gitpod
+
+# Install custom tools, runtime, etc. using apt-get
+# For example, the command below would install "bastet" - a command line tetris clone:
+#
+# RUN sudo apt-get -q update && \
+#     sudo apt-get install -yq bastet && \
+#     sudo rm -rf /var/lib/apt/lists/*
+#
+# More information: https://www.gitpod.io/docs/config-docker/
+
+RUN bash -c ". /home/gitpod/.sdkman/bin/sdkman-init.sh && sdk install java 8.0.292.hs-adpt"