use libuv event loop in the glfw view

Integrates libuv's default loop with GLFW's glfwWaitEvents() call. See https://github.com/joyent/libuv/issues/1246 for more details on integrating event loops.

fixes #149

include/llmr/platform/platform.hpp

@@ -38,9 +38,6 @@ void cancel_request_http(const std::shared_ptr<Request> &req);
 // Returns a relative timestamp in seconds. This value must be monotonic.
 double elapsed();
 
-// Performs routine cleanup operation and is called on every loop iteration.
-void cleanup();
-
 // Shows an RGBA image with the specified dimensions in a named window.
 void show_debug_image(std::string name, const char *data, size_t width, size_t height);