Fixed division problem in MCP3004. 

Should be 10.23 as 11 11111111 is 1023 not 1024. 
1023 / 10.24 = 99.90234375 instead of 100. 

Can create small variance in percentage returned.

For example ADC bits of 10 1110 0110 (742) : 

Python 2.7.5 console:

>>> int(round(742/10.23))
73
>>> int(round(742/10.24))
72