Adding how the I2C parsing works

For myself and my future self

Author: nseidle

Theory.md

@@ -0,0 +1,13 @@
+How I2C library works
+===========================================================
+
+When the user calls one of the methods the library will poll the Ublox module for new data. 
+
+* Wait for a minimum of 25 ms between polls (configured dynamically when update rate is set)
+* Write 0xFD to module
+* Read two bytes (0xFD and 0xFE) for bytes available
+* If 0x7F or 0xFF then no bytes are available
+* Otherwise, read number of bytes and process into NMEA, UBX, or RTCM frame.
+* If checksum is valid, flag frame as complete.
+
+