Fixed I2C 7-Bit Addressing

The TwoWire Library expects slave addresses to be entered in the
standard 7-Bit format. Added some code to the I2C_Send7bitAddress
function so that the address is bitshift to the left by one, before
performing the bitwise operation to set the R/W bit. See: https://community.sparkdevices.com/t/i2c-7-or-8-bit-addresses/1328/9