Use relative links in README to ensure they go to the correct branch

Author: 0b10011

README.md

@@ -17,7 +17,7 @@ Develop:
 
 PHPWord is a library written in pure PHP that provides a set of classes to write to and read from different document file formats. The current version of PHPWord supports Microsoft [Office Open XML](http://en.wikipedia.org/wiki/Office_Open_XML) (OOXML or OpenXML), OASIS [Open Document Format for Office Applications](http://en.wikipedia.org/wiki/OpenDocument) (OpenDocument or ODF), [Rich Text Format](http://en.wikipedia.org/wiki/Rich_Text_Format) (RTF), HTML, and PDF.
 
-PHPWord is an open source project licensed under the terms of [LGPL version 3](https://github.com/PHPOffice/PHPWord/blob/develop/COPYING.LESSER). PHPWord is aimed to be a high quality software product by incorporating [continuous integration](https://travis-ci.org/PHPOffice/PHPWord) and [unit testing](http://phpoffice.github.io/PHPWord/coverage/develop/). You can learn more about PHPWord by reading the [Developers' Documentation](http://phpword.readthedocs.org/).
+PHPWord is an open source project licensed under the terms of [LGPL version 3](COPYING.LESSER). PHPWord is aimed to be a high quality software product by incorporating [continuous integration](https://travis-ci.org/PHPOffice/PHPWord) and [unit testing](http://phpoffice.github.io/PHPWord/coverage/develop/). You can learn more about PHPWord by reading the [Developers' Documentation](http://phpword.readthedocs.org/).
 
 If you have any questions, please ask on [StackOverFlow](https://stackoverflow.com/questions/tagged/phpword)
 
@@ -174,7 +174,7 @@ You can also read the [Developers' Documentation](http://phpword.readthedocs.org
 
 We welcome everyone to contribute to PHPWord. Below are some of the things that you can do to contribute.
 
-- Read [our contributing guide](https://github.com/PHPOffice/PHPWord/blob/master/CONTRIBUTING.md).
+- Read [our contributing guide](CONTRIBUTING.md).
 - [Fork us](https://github.com/PHPOffice/PHPWord/fork) and [request a pull](https://github.com/PHPOffice/PHPWord/pulls) to the [develop](https://github.com/PHPOffice/PHPWord/tree/develop) branch.
 - Submit [bug reports or feature requests](https://github.com/PHPOffice/PHPWord/issues) to GitHub.
 - Follow [@PHPWord](https://twitter.com/PHPWord) and [@PHPOffice](https://twitter.com/PHPOffice) on Twitter.