Fix error message so it reflects actual error rather than that for shouldContainText.
Modify shouldContainText so that error message shows both the expected text, and the text found in the element.
Add containsOnlyText and shouldContainOnlyText methods. Similar to containText, exact performs an exact match.
Updated version numbers
Merge branch 'master' of https://github.com/mikezx6r/thucydides
Upgraded to Selenium 2.31.0