* moved aws elasticache module to boto3
* fixed error and improved code
* implemented requested changes
* now checking for missing boto3 packages in a better way
* now dynamically setting the default port depending on the engine if it is not set
* moved standard import in front of ansible ones
* now case insensitive in regards to engine name
* removed superfluous spaces
* now checking for None in the correct way
* removed elasticache module from exceptions to pep8 testing
* removed hardcoded default ports and letting aws decide if no port is given
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