Complement list of missing standard Lua modules

Author: marcelstoer

README.md

@@ -14,7 +14,7 @@ The firmware was initially developed as is a companion project to the popular ES
 # Summary
 
 - Easy to program wireless node and/or access point
-- Based on Lua 5.1.4 (without `debug` & `os` modules)
+- Based on Lua 5.1.4 but without `debug`, `io`, `os` and (most of the) `math` modules
 - Asynchronous event-driven programming model
 - more than **65 built-in modules**
 - Firmware available with or without floating point support (integer-only uses less memory)