[LIBCLOUD-535] Add EbsOptimized parameter to create_node() method
of BaseEC2NodeDriver in ec2.py driver

[LIBCLOUD-535] Fix parameter name add documentation
Merge branch 'LIBCLOUD-535_create-EBS-Optimized-instance' of https://github.com/zerthimon/libcloud into LIBCLOUD-535_create-EBS-Optimized-instance