Refactoring code and documentation

[130s]

This PR is basically refactoring only. These 2 commits include the most changes:

• https://github.com/corb555/iot_bridge/pull/7/commits/13cb1ca16b4c0f754283e0a64cf497458869eaac Code cleaning. More conformation to Python coding style PEP8 that include replacing tabs with spaces and 80 chars per line.
• https://github.com/corb555/iot_bridge/pull/7/commits/3ee7c72513f06780512ef27eacd2a52e493b6efd [doc] Fully utilize rosdoc_lite to auto-generate docs on ros.org server from .rst, so that we can maintain document at one location (i.e. here, Github repo) but still can propagate the doc on ros.org. Also added a bit more doc content.