Nc element xml usability

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https://travis-ci.org/francisluong/ncclient/builds/29464926

This change started with me not being able to get indented output from result.tostring.  So, I modified that by creating a custom parser per http://lxml.de/FAQ.html#why-doesn-t-the-pretty-print-option-reformat-my-xml-output

Then I figured I'd add the ability to also str(result) for the same output.  And I added result.findtext().

Then I decided to add nose tests for my changes.  See the test/ folder.

Then I added a .travis.yml so we could do some CI.

That's about it.