Added clang-format config

Change-Id: I78676ab1f51f601f15a72ee168cb9f04eee04788
Reviewed-on: https://weave-review.googlesource.com/1736
Reviewed-by: Alex Vakulenko <avakulenko@google.com>

.clang-format

diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..685c597
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,5 @@
+---
+Language:        Cpp
+# Usage:  git clang-format -f m/master --style=file
+BasedOnStyle:  Chromium
+...