Create README.md
Update README.md
Update README.md
Update CalculatorDemoTests.cs

Commented out web drivers for IE and Firefox.  Only chrome is shown in this simple demo.  These can be uncommented to demo a run against FireFox and IE.
Update CalculatorDemoTests.cs
Merge pull request #2 from BadLambdaJamma/master

Created a readme file that explains the prerequisites. Commented out the web drivers for FireFox and IE