Updated to addressthe  change in the Nexmo api (username => api_key,
password => api_secret)
Updated CURL OPT CURLOPT_SSL_VERIFYHOST to 2, as 1 is now deprecated 
Added the ability to debug the request
Merge pull request #2 from el-timm/master

API change to Nexmo parameters, added ability to debug the request, and migrate from deprecated CURLOPT_SSL_VERIFYHOST value