Update Fedora Badges SOP for 2018 best practices
    
    This is a huge commit for this document and makes a number of changes.
    I've split them up into two sections: content and style. By making this
    PR, I am also accepting a conditional responsibility for maintaining
    this content too. :P
    
    Content
    -------
    
    * **Existing content**:
        * Update invitation instructions for user email instead of ID
        * Update some broken links
    * **New content**:
        * Completely rework section on pushing badges; aggregated
          information from a variety of sources ¹ ² ³
    
    Style
    -----
    
    * Follow one-sentence per line convention for easier git diffs
    * Insert more links and create an appendix for commonly-used links
    * Follow ReStructuredText style guide for headers
    * Generally make content easier to read when rendered with better markup
      (will be helpful especially for Flock Badges sysadmin workshop)
    * Other small, trivial changes
    
    ¹ https://pagure.io/fedora-docs/quick-docs/pull-request/36
    ² https://pagure.io/fedora-badges/pull-request/617
    ³ https://blog.justinwflory.com/2016/07/push-fedora-badges/