Add quote string option to tokenizer.

include/string_utils/tokenizer.h

@@ -18,13 +18,14 @@ public:
   static constexpr size_t const infinite_outputs{~size_t(0)};
 private:
   std::string divider_;
+  std::string quotes_;
   size_t max_outputs_{infinite_outputs};
   bool truncate_{false};
   bool ignore_empty_tokens_{true};
   bool escapable_{false};
 
 public:
-  tokenizer(std::string const & divider);
+  tokenizer(std::string divider, std::string quotes = "");
     
   tokenizer &max_outputs(size_t new_max_outputs);
   tokenizer &truncate(bool new_truncate_overage);

src/tokenizer.cxx

@@ -10,7 +10,8 @@
 
 namespace string_utils {
 
-tokenizer::tokenizer(std::string const & divider) : divider_(divider) {}
+tokenizer::tokenizer(std::string divider, std::string quotes)
+  : divider_(std::move(divider)), quotes_(std::move(quotes)) {}
 
 tokenizer &tokenizer::max_outputs(size_t new_max_outputs) {
   max_outputs_ = new_max_outputs;