Apply clang-format to all headers and source (#303)

diff --git a/src/string_util.h b/src/string_util.h
index b89fef5..0b190b9 100644
--- a/src/string_util.h
+++ b/src/string_util.h
@@ -1,8 +1,8 @@
 #ifndef BENCHMARK_STRING_UTIL_H_
 #define BENCHMARK_STRING_UTIL_H_
 
-#include <string>
 #include <sstream>
+#include <string>
 #include <utility>
 #include "internal_macros.h"
 
@@ -14,23 +14,19 @@
 
 std::string StringPrintF(const char* format, ...);
 
-inline std::ostream&
-StringCatImp(std::ostream& out) BENCHMARK_NOEXCEPT
-{
+inline std::ostream& StringCatImp(std::ostream& out) BENCHMARK_NOEXCEPT {
   return out;
 }
 
-template <class First, class ...Rest>
-inline std::ostream&
-StringCatImp(std::ostream& out, First&& f, Rest&&... rest)
-{
+template <class First, class... Rest>
+inline std::ostream& StringCatImp(std::ostream& out, First&& f,
+                                  Rest&&... rest) {
   out << std::forward<First>(f);
   return StringCatImp(out, std::forward<Rest>(rest)...);
 }
 
-template<class ...Args>
-inline std::string StrCat(Args&&... args)
-{
+template <class... Args>
+inline std::string StrCat(Args&&... args) {
   std::ostringstream ss;
   StringCatImp(ss, std::forward<Args>(args)...);
   return ss.str();
@@ -39,6 +35,6 @@
 void ReplaceAll(std::string* str, const std::string& from,
                 const std::string& to);
 
-} // end namespace benchmark
+}  // end namespace benchmark
 
-#endif // BENCHMARK_STRING_UTIL_H_
+#endif  // BENCHMARK_STRING_UTIL_H_