v1.0.0

This release:

1. Consolidates all options under the options key, those for the executable at the top level and those for simple-cli itself under simple.
2. Removes the stdio option, replacing it with an onComplete handler that receives the stderr and stdout.
3. Adds an env option for specifying additional environment variables.
4. Splits up cmd and args into separate options and allows an array for args
5. Adds a debug flag.
6. Adds an extensibility mechanism for custom options.
7. Allows dynamic values to be specified via grunt.config.