Add additional checking for binary data

Use the bytesarray type added in Python 2.6 to signify that this is
binary data and to quote it accordingly. Also modify the handling of
str/bytes types checking the first 2 characters for b'0x' and insert
that as binary data.
Fix converting bytearray to hex on Python 2.6

In py26 it's not possible to pass a bytearray directly into hexify
so convert it to bytes first before passing it in.
Merge pull request #179 from pymssql/fix-encoding-binary-data

Add additional checking for binary data (fix for #177)