Add interactive mode (#61)

* Initial work on interactive mode.

* Improve interactive mode. Make rev. prompt optional.

* Update README to explain interactive mode.

* Fix OS X build

utils.h

@@ -28,6 +28,12 @@ struct gpt_params {
 
     std::string model = "models/lamma-7B/ggml-model.bin"; // model path
     std::string prompt;
+
+    bool use_color = false; // use color to distinguish generations and inputs
+
+    bool interactive = false; // interactive mode
+    bool interactive_start = false; // reverse prompt immediately
+    std::string antiprompt = ""; // string upon seeing which more user input is prompted
 };
 
 bool gpt_params_parse(int argc, char ** argv, gpt_params & params);