Update plugin to operate with Stackstorm 1.5

[nzlosh]

Please consider the following patch sets for integration with your repository.

The patches include the following:

• Update support so config.py files can specify authentication information.
• Authentication against the Stackstorm API with either username/password or user token.
• When using username/password, the user token is renewed automatically.
• Handle action aliases in the form of string or dictionary with display and representation.
• Accept default values for named arguments, accept extra key/value pair arguments.

Sorry for the large patch set, I wasn't intending on creating a pull request initially.

[fmnisme]

This is a very good pull request, thank you for improve this project ^_^