Delimiter-aware RegEx in Attributes

See https://github.com/techtalk/SpecFlow/issues/309

I have used the * based RegEx patterns for single and double quotes as they most closely match the default pattern.

This should be a good solution for Issue 309 - although it may not be the most graceful version of the fix. I'm happy to be led in this respect as this is my first commit to SpecFlow. I am also having to force things to work on my machine, which won't let me install some of the developer dependencies as I have newer versions installed - I'm also working in "Target 4.0" mode and reverting to "Target 3.5" for check ins.

All tests in "RuntimeTests" pass.