replace boost filesystem with std filesystem; upgrade gtest and find it using cmake.

webcc/string.h

@@ -0,0 +1,28 @@
+#ifndef WEBCC_STRING_H_
+#define WEBCC_STRING_H_
+
+#include <algorithm>
+#include <iterator>
+#include <sstream>
+#include <string>
+
+namespace webcc {
+namespace string {
+
+// Get a randomly generated string with the given length.
+std::string RandomString(std::size_t length);
+
+// TODO: What about std::wstring?
+bool EqualsNoCase(const std::string& str1, const std::string& str2);
+
+template <class Container>
+void Split(const std::string& str, Container& cont) {
+  std::istringstream iss(str);
+  std::copy(std::istream_iterator<std::string>(iss),
+            std::istream_iterator<std::string>(), std::back_inserter(cont));
+}
+
+}  // namespace string
+}  // namespace webcc
+
+#endif  // WEBCC_STRING_H_