Fixed a typo in README.md

I added `"easysoap": "0.5.0"` in my package.json file
And I ran `npm install`
Then I tried to run the server but got

````
Warning: Cannot find module 'easySoap' Use --force to continue.

Aborted due to warnings.
    Warning:  Use --force to continue.
        
        Aborted due to warnings.
````

The problem was fixed by typing the module name in all lower case in the require.