Update README.rst

Removed wrong indent
Changed to use rpm instead of yum

Fixes tnc-ba/strongTNC/issues/108

Removed debug print

Removed dependency section from Readme

Renamed environment from yum to rpm
Updated README changed yum to rpm
Changed --environment option to be rpm
Added visitor to print output, no caching in list anymore
Moved document_separator to visitor
Cleaned up comments
Removed debug print
Style fixes + print function

- Imported print function
- Removed unnecessary parens from from if
- Removed unused import
Added file encoding header
Changed identation of pretty output from tab to two spaces

Fixes https://github.com/tnc-ba/swidGenerator/issues/14
Removed extra newline from software-id mode

Fixes https://github.com/tnc-ba/swidGenerator/issues/15
Removed visitor pattern and introduced generators

- Introducing generators allows lazy generation of software-ids and SWID
tags
- Removed print visitor. Output printing is now done with a print function which takes the generator
Added exit code 1 if no package is found

fixes https://github.com/tnc-ba/strongTNC/issues/104