MQTT on ESP8266 with Espruino

@Kolban the guys from nodemcu had the same problem and fixed it. Heap doubled from one day to the other.
@Gordon source is available here http://jumspruino.jumware.com/sources/SHA1.js.
I did some (crazy) things to reduce memory and speed, which did not make it easier to read:

• use typed arrays
  
• remove temporary values
  
• replace switch by if...elseif...
  
• removed functions and added code inline
  
• reuse local vars
  
• converted multiplication(like *4, *32,..) to shift
  
• removed a "funny" encode64 and use btoa instead
  
• moved functions to be local
  All together my plan is to use ESP8266 for web, and let Espruino boards do the hard work.