Add config parameter for the api listening socket

Add api_host and api_port in 'site' section of the config
Bind the api according to config

Use api_host and api_port from config instead of hardcoded values
Update api.py

Use default values for socket binding if the config file does not contain user specified values.
Merge pull request #44 from guillp/api-binding

Api socket binding config
Merge branch 'master' into development