add gmp so that docker images build correctly

Dockerfile

@@ -8,6 +8,11 @@ ENV DEBCONF_NOWARNINGS yes
 ENV TERM linux
 RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
 
+RUN apt-get update && \
+  apt-get install -y --no-install-recommends \
+    libgmp3-dev && \
+  rm -rf /var/lib/apt/lists/*
+
 # Install go
 # ADD tendermint user
 RUN useradd tendermint