Minor Grammatical Fixes to README.md

Make minor grammatical fixes to README.md
- 'Here's some more demos' to 'Here are some more demos'
- 'Some services...In such case' to 'Some services...In such cases, '

![hello js pull request](https://cloud.githubusercontent.com/assets/5909572/4330756/67aadb6e-3fb5-11e4-9f0f-beed0374a4aa.png)