Simplify the build instructions now that Netty can be fetched from Maven

.gitmodules

@@ -1,3 +0,0 @@
-[submodule "lib/netty"]
-	path = lib/netty
-	url = https://github.com/netty/netty.git

README.md

@@ -116,16 +116,6 @@ How to Build
 ------------
 This section is only necessary if you are making changes to gRPC-Java.
 
-### Build Netty
-grpc-java requires Netty 4.1, which is still in flux. The version we need can be
-found in the lib/netty submodule, which requires Maven 3.2 or higher to build:
-```
-$ git submodule update --init
-$ cd lib/netty
-$ mvn install -pl codec-http2 -am -DskipTests=true
-```
-
-### Build gRPC
 Building requires JDK 8, as our tests use TLS.
 
 grpc-java has a C++ code generation plugin for protoc. Since many Java

buildscripts/make_dependencies.sh

@@ -17,21 +17,3 @@ else
   make install
   popd
 fi
-
-# Make and install netty
-pushd lib/netty
-BUILD_NETTY=1
-NETTY_REV_FILE="$HOME/.m2/repository/io/netty/netty-ver"
-REV="$(git rev-parse HEAD)"
-if [ -f "$NETTY_REV_FILE" ]; then
-  REV_LAST="$(cat "$NETTY_REV_FILE")"
-  if [ z"$REV" = z"$REV_LAST" ]; then
-    BUILD_NETTY=0
-    echo "Not building Netty; already at $REV"
-  fi
-fi
-if [ $BUILD_NETTY = 1 ]; then
-  mvn install -pl codec-http2 -am -DskipTests=true
-  echo "$REV" > "$NETTY_REV_FILE"
-fi
-popd

lib/netty

@@ -1 +0,0 @@
-Subproject commit 871ce43b1f431536e08a36d420875494ef3e9451