Some CLI Cleanup/Housekeeping

This pull request is to make things a bit nicer. For example:

    $ sl
    usage: sl {help,list,cci,dns,firewall,list}
    sl: error: too few arguments

is now:

    $ sl
    usage: sl [-h] [{cci,dns,firewall,help}]
    
    SoftLayer Command-line Client
    
    positional arguments:
      {cci,dns,firewall,help}
                            Module name, try help or list

Detail:

* CLI: `sl` no longer outputs an error saying you didn't provide enough arguments. Instead, it prints the help.
* CLI: Adds 'importlib' as a requirement for Pythons < 2.7
* CLI: When executing the given command. pressing Ctrl + C will not spit out an ugly exception.
* CLI: Mass re factoring.
    * The code from bin/sl was moved into SoftLayer/CLI/__init__.py
    * Organizes test code.
* CLI: More testing for CLI code. Argument Parsing. Configuration Reading.
* CLI: Adds README.md and LICENSE to manifest so they will be packaged for distribution.