More coverity fixes

Marlin/Marlin_main.cpp

 
         if(pin_state >= -1 && pin_state <= 1){
 
-          for(int8_t i = 0; i < (int8_t)sizeof(sensitive_pins); i++)
+          for(int8_t i = 0; i < (int8_t)(sizeof(sensitive_pins)/sizeof(int)); i++)
           {
             if (sensitive_pins[i] == pin_number)
             {

Marlin/temperature.cpp

       SERIAL_ERROR((int)e);
       SERIAL_ERRORLNPGM(" - Invalid extruder number !");
       kill();
+      return 0.0;
   } 
   #ifdef HEATER_0_USES_MAX6675
     if (e == 0)

README.md

 ==========================
 Marlin 3D Printer Firmware
 ==========================
+[![Coverity Scan Build Status](https://scan.coverity.com/projects/2224/badge.svg)](https://scan.coverity.com/projects/2224)
+
 Marlin has a GPL license because I believe in open development.
 Please do not use this code in products (3D printers, CNC etc) that are closed source or are crippled by a patent.