Add 100 column limit to .clang-format.

Change-Id: I3c3fa5e61cfb2af7f2888dcee56229692ec1479c
diff --git a/.clang-format b/.clang-format
index ea19538..9b7478c 100644
--- a/.clang-format
+++ b/.clang-format
@@ -2,6 +2,7 @@
 AllowShortBlocksOnASingleLine: false
 AllowShortFunctionsOnASingleLine: false
 
+ColumnLimit: 100
 CommentPragmas: NOLINT:.*
 DerivePointerAlignment: false
 IndentWidth: 2