Fix problem with reading hot humid conditions

Previously, if the calculated checksum was > 255 (commonly encountered in hot, humid conditions), the extra bit wasn't dropped, causing the checksum to fail every time.
Fix problem with reading hot humid conditions

Previously, if the calculated checksum was > 255 (commonly encountered in hot, humid conditions), the extra bit wasn't dropped, causing the checksum to fail every time.
Create MAX31855.js

Module for interfacing with MAX31855 thermocouple controller.
Create MCP4xxx.js
Update MAX31855.js

Fix cs pin not being used, temp code being returned in fault conditions.
MAX31855.md
Delete MCP4xxx.js

Not ready yet.
Merge pull request #85 from SpenceKonde/master

Fix DHT modules to work in summer, add MAX31855 module