Removed maxConnections and maxMessages

Removed instances of maxConnections and maxMessages in the code snippets of the readme, as according to the smtp-transport-pool readme.md, they are what differentiates the two. Quoted from smtp-transport-pool readme: "Pooled SMTP transport uses the same options as SMTP transport __with the addition__ of maxConnections and maxMessages."
Merge pull request #5 from VAS/patch-1

Removed maxConnections and maxMessages