Merge pull request #1511 from General-Beck/patch-17

Update Ubuntu-jit Dockerfile

docker/ubuntu-jit/Dockerfile

@@ -47,7 +47,7 @@ g++ -v
 # build parity
 RUN git clone https://github.com/ethcore/parity && \
         cd parity && \
-        git checkout master && \
+        git checkout beta && \
         git pull && \
         cargo build --release --features ethcore/jit --verbose && \
         ls /build/parity/target/release/parity &&       \