Add Tree::TreeNode.from_hash and #add_from_hash
Add tests for #from_hash and #add_from_hash
Override #add_from_hash on Tree::BinaryTreeNode

Unlike the general N-ary case, we need to ensure we don't add more than two
children to a node on a binary tree.
Move Hash conversion methods into a util file.
Add #to_h function, doc tweaks.
Restore license accidentally removed from json_converter.
Correctly recurse print_tree method
Merge pull request #34 from packetmonkey/fix_print_tree

Correctly recurse print_tree method
Merge pull request #30 from jhamon/from_hash

Add mixin for Hash conversions. Thanks to @jhamon.
Fixed the file name in documentation.
Added the copyright banner, and minor documentation fixes.
Fixed issue#31.

The methods `postordered_each` and `breadth_each` were behaving incorrectly when
a block was not provided.
Updated the dependent gems.
Updated the Yard dependency.
Updated the documentation to 0.9.5pre.