Add support for processing instructions

Closes #32 - Add support for processing instructions.

Developer experience updates

Updates to phpDoc, namespaces and Travis-CI settings.

News subelement

#25 - Add news subelement. Thanks @sherault

Otto, README and Composer changes

• Add otto Appfile, can now develop against the library by running otto dev
• Removed composer.lock, not technically required for libraries.
• Add Links subelement to the README

Add Links Subelement

#19 - Thanks to @marcw for adding support for the Links subelement.

Run tests through composer

Merge pull request #16 from hkdobrev/composer-test

Use composer test script to run tests

Use getPlayerLoc in Video Sitemap

4.1.1

Use getPlayerLoc in Video Sitemap

New Subelements

• Mobile Sitemap
• Video Sitemap
• Updated README with more examples

Fix PHP warning

#14 - Default sub elements property to an empty array

Updated README

Fixed the travis-ci image and cleaned up the examples