Update README.md

Hi,
I've been learning this mock framework these days. When I read the README file I found two missing links for the word "here" in the "Remember" part :
1. link to more documentation and examples
2. link to RefCard 
so I did these micro-modifications. I hope this will be helpful for you. 

Kuangshi
Merge pull request #58 from yankuangshi/patch-1

Update README.md with better links and documentation