Calibration, Simplified Get commands, Bug Fixes

• Calibration
  • Somewhat of a large feature addition to assist with calibration. The HX711 class now includes a function to launch a sequence to help with calibration. This is something that needs to be performed in almost all cases, so adding this functionality should help during the setup process. The calibration sequence prompts the user to confirm known weights and then calculates a weight multiple based on the measurements and those known weights.
• Get Commands
  • Due to confusion about how the read_raw() and read_weight() functions work, I added get_raw() and get_weight() to clarify when a new measurement will or will not be taken.
• Bugs
  • I found some bugs when the user supplies an integer for the dout_pins (this is a supported feature). This was supposed to allow the user to run hx711-multi with only a single ADC and not force them to use list indexing everywhere, but a bug made a small part of it not work. I fixed that bug and now you can use hx711-multi without the "multi" functionality if you pass an integer for the dout_pins input.