Remove progress file, update README

Progress

@@ -1,23 +0,0 @@
-http://dev.minetest.net/formspec
-
-size:               Done!
-list:               Incomplete
-image:              image
-field:              textbox
-pwdfield:           textbox
-textarea:           textbox
-label:              text
-vertlabel:          text
-button:             button
-image_button:       button
-item_image_button:  button
-button_exit:        button
-image_button_exit:  button
-listcolors:         formspeclib:raw_formspec
-bgcolor:            formspeclib:raw_formspec
-background:         formspeclib:raw_formspec
-textlist:           combobox
-dropdown:           combobox
-
-Incomplete:
-list

README.md

@@ -1,3 +1,4 @@
 # formspeclib
 
-A formspec renderer for Minetest.
+A formspec renderer for Minetest. Currently, all the documentation is in
+comments inside `core.lua` and `objects.lua`.