CFY-1739 Added *Salt* plugin's description and documentation
fixup! CFY-1739 Added *Salt* plugin's description and documentation
fixup! CFY-1739 Added *Salt* plugin's description and documentation
fixup! CFY-1739 Added *Salt* plugin's description and documentation

Rewrote the installation procedure description.
fixup! CFY-1739 Added *Salt* plugin's description and documentation

Synchronised with the plugin's README file.
Merge pull request #207 from codilime/CFY-1739-salt-plugin-doc

Salt plugin's description and documentation