Updated version to avoid confusion.
Made changes for generics across the board.
Revert "Made changes for generics across the board."

This reverts commit cdf8d74bac3442a0a882c3831123f4c2e6d27bfc.
Changed getChild to make things easier to work with.
Updated NXStringNode to take advantage of method return covariance.
Updated NXPointNode to take advantage of method return covariance.
Updated NXLongNode to take advantage of method return covariance.
Updated NXDoubleNode to take advantage of method return covariance.
Updated NXBitmapNode to take advantage of method return covariance.
Updated NXAudioNode to take advantage of method return covariance.
Flattened format package.
Made populateChildren() on NXNode package-private.
Updated node version numbers according to covariance updates.
Changed version to 3.0.0.Snapshot.
Renamed NXFile to StrictNXFile.
Added an abstract NXFile interface.
Made some changes to the README for transparency.
Officially targeting Java 7.
Updated dependencies to latest versions.
Limited guava to test scope.