[#293] Make new method public

- Since it's being invoked as a static callback, the method needs to be
  public. Renamed to remove the underscore prefix, and marked as public.
[#293] Ensure Zend\Xml tests pass on PHP 5.2

- Prior to 5.3, you needed to cast a simplexml node to a scalar in order
  to do comparisons.
[#293] Update .gitignore rules

- Discovered on installing PHPUnit to run tests that .gitignore was not setup to
  ignore composer.lock, nor the files installed in the bin/ directory.
Merge branch 'hotfix/293'

Fixes issues seen in #293