Reconcile comment section with the elisp reference

(Mostly) fix #2.

This commit just fixes the parts where this style guide diverged from
the elisp reference. It doesn't do anything about the sentence-ending
discussion in #2.
Merge pull request #19 from Bruce-Connor/semicolons

Reconcile comment section with the elisp reference
Move the if indentation rule to the code layout section
Correct "issues" link.
Merge pull request #21 from mwfogleman/contributing

Correct "issues" link.
Add a Docstrings section.
Add a blank line between items for consistency.
Merge pull request #22 from mwfogleman/docstrings

Add a Docstrings section.