fix documentation issue.
initial implementation of --config option.
added --config to specify config file location
if not specified, the program will first look for the path $PWD/crowdutil.json (as before), but also looks for $HOME/.crowdutil/config.json (or %USERPROFILE%\.crowdutil\config.json for windows) if $PWD/crowdutil.json is not found.
also changed the default path for create-config file to $HOME/.crowdutil/config.json when -o is not specified (minor incompatibility).
All changes except the create-config default location should be backwards compatible.