Implemented Issue #13 - Add reader mode information to reader object

[beamerblvd]

Re-do of pull request #14. Implemented issue #13. Also rebased to master so that it's merge-able. Compiled libmaxminddb locally, compiled maxminddb.extension against it locally, and tested with all modes explicit and with MODE_AUTO. Works great!

My only concern now is that, in pull request #14, I could access the mode with this:

reader.metadata().mode

But now I have to do this:

reader._db_reader.mode

That's violating best practices by accessing a "private" variable. Suggestions?

[beamerblvd]

So I don't really understand the output of the failed builds. If I need to fix something, let me know. I do know that it compiles and works on my machine, but I also know that isn't enough.

[oschwald]

Although we are open to a PR along these lines, this appears to be causing segmentation faults under Travis. Also, new additions such as this should have unit tests.

[oschwald]

Closing due to inactivity. It would be nice to expose the metadata though so please feel free to reopen once the segmentation faults are resolved.