Add Renew and GetPricing methods

Add a few more official Namecheap supported methods to the API.
I noticed your version of the API was missing a few commands I planned on using, so I added them. I followed your formatting, and also added examples to the correct directory.
Seems like docBlock have some small issues. 

Domain is limited to 70 chars and also domainName is of type of string, but not array.