Cast handling fixed

[iuliux]

This should fix Issue #6

A new config option is added, objCastMode which can take values drop or ctor

[natural]

Thank you for the code. I truly appreciate the thought and effort.

I'm going to go ahead and merge this, however, there are two things that need to happen afterwards:

1. I don't like "modes", basically controlling behavior via keywords; I prefer callable objects that the user can then specify
2. There aren't any tests, but that's easily enough to fix.

I'll work on the changes after the merge. Again, many thanks.

[iuliux]

Thank you for the merge.

About the test, I couldn't figure out how tests work (how they assert the result, how to run them). I think that an additional doc about this would be very welcome.

Some other issue that came out from testing this is with regard to java wrapper types (but I'll open a new ticket for this)

[natural]

Added docs for tests.