Added client encoding to adapted SQL parameters.

[osvill]

Fix & test for #158 .

[palewire]

This is an awesome start. Would it be possible to run a test that raises the encoding error so we can verify the reverse circumstance here?

[osvill]

It is hard to catch the error as a specific encoding error. I ended up adding a keyword argument client_encoding and raising a ValueError if client_encoding does not match the database encoding (2nd commit). What do you think?

[osvill]

I ran some more tests and got errors for adapted parameters that do not have the encoding attribute. Therefore I added the hasattr check and the test filtering by a number in the 3rd commit.