Dev master

This accomplishes several changes:
- Adds ADC block that can read from an SPI ADC chip
  - not ready for production yet -- need to add modes to allow for I2C chips and other options. We don't yet have an I2C chip picked out
- Significant (and backward incompatible) updates to the Rio object. Makes it much easier to use.
  - read and write blocks now use the Rio module
- Added a bunch of options for pins in output mode. These are:
  - mode -- allows each pin to select whether it wants to use pull resistors
  - initial -- allows you to set an initial value (True or False).
    - if pullups are on, initial reflects whether it will be up (True) or down (False). The Rio module makes this very simple
- Unit tests have been created and used to verify that module works as intended