Release/1.2

[ReagentX]

• Better filter logic when sending network sensor data to DataFrames for #49
• Add filters for sensors with and without children for #49
• Better error formatting when given bad or missing data
• Update sample code and documentation for to_dataframe, add notes about Channels
• Fix bug where the library attempted to get Statistics data from the wrong field
• Rename 'a' and 'b' to 'parent' and 'child' throughout app
• Add missing ADC, RSSI, and 1day_avg fields to data exports for #51
• Add as_dict and as_flat_dict as Channel methods for #52
• Add as_list to Sensor methods
• Simplify logic for as_dict and as_flat_dict for Sensor