Merge pull request #2 from phantomwhale/master

Xpath extractor
Support for Xpath and Regex extractors via one method
Support for Xpath and Regex extractors via one method
Updated README
Merge pull request #3 from phantomwhale/master

Allow override of URI parameters in the HTTP Sampler
Updated README (override URI params)
Updated README (default selector for extract method)
Updated README (default selector for extract method)
Typo in example