Fixed mesos-tidy build with new gRPC version. (#451)

And updated gRPC 3rdparty documentation to reflect updated version.
diff --git a/3rdparty/grpc.md b/3rdparty/grpc.md
index 4430e1f..6acb670 100644
--- a/3rdparty/grpc.md
+++ b/3rdparty/grpc.md
@@ -14,7 +14,7 @@
 
 ## Bundled Version
 
-We bundle 1.10.0 for better CMake build support.
+We bundle 1.11.1 for better CMake build support, and s390x support.
 
 ## Cherry Picks
 
@@ -29,11 +29,3 @@
 - [CMake: Automatic fallbacking on system's OpenSSL if it only has NPN.](https://github.com/chhsia0/grpc/commit/5c13ad2a3df1108184c716379818eab6fc0ba72d)
 
   Upstream PR: https://github.com/grpc/grpc/pull/17726
-
-- [Fix gettid() naming conflict.](https://github.com/grpc/grpc/commit/de6255941a5e1c2fb2d50e57f84e38c09f45023d)
-
-  Upstream PR: https://github.com/grpc/grpc/pull/20048
-
-- [Rename gettid() functions.](https://github.com/grpc/grpc/commit/57586a1ca7f17b1916aed3dea4ff8de872dbf853)
-
-  Upstream PR: https://github.com/grpc/grpc/pull/18950
diff --git a/support/mesos-tidy/entrypoint.sh b/support/mesos-tidy/entrypoint.sh
index 8bdd1ec..03d6b6a 100755
--- a/support/mesos-tidy/entrypoint.sh
+++ b/support/mesos-tidy/entrypoint.sh
@@ -43,7 +43,7 @@
 cmake --build 3rdparty --target elfio-3.2
 cmake --build 3rdparty --target glog-0.4.0
 cmake --build 3rdparty --target googletest-1.8.0
-cmake --build 3rdparty --target grpc-1.10.0
+cmake --build 3rdparty --target grpc-1.11.1
 cmake --build 3rdparty --target http_parser-2.6.2
 
 # TODO(mpark): The `|| true` is a hack to try both `libev` and `libevent` and