Update Dockerfile

Update CentOS Dockerfile
[ci skip]

docker/centos/Dockerfile

@@ -2,24 +2,26 @@ FROM centos:latest
 WORKDIR /build
 # install tools and dependencies
 RUN yum -y update&& \
-    yum install -y git make gcc-c++ gcc file 
+    yum install -y git make gcc-c++ gcc file binutils
 # install rustup
 RUN curl -sSf https://static.rust-lang.org/rustup.sh -o rustup.sh &&\
 ls&&\ 
  sh rustup.sh -s -- --disable-sudo
 # show backtraces
 ENV RUST_BACKTRACE 1
+# set compiler
 ENV CXX g++
 ENV CC gcc
+# show tools
 RUN rustc -vV && \
 cargo -V && \
 gcc -v &&\
 g++ -v
-# git clone parity
+# build parity
 RUN git clone https://github.com/ethcore/parity && \
 	cd parity&&\
         ls -a&&\
         cargo build --release --verbose && \
 	ls /build/parity/target/release/parity &&	\
-	file /build/parity/target/release/parity && \
+	strip /build/parity/target/release/parity
 RUN file /build/parity/target/release/parity