Use `code` instead of _italics_ for file names
Clarify file name
Give symmetry to emdash
Fix typo
Revert "Use `code` instead of _italics_ for file names"

This reverts commit ca85fd43d14e144e63915efec1929311a858e01d.

See discussion in pull request:
https://github.com/github/developer.github.com/pull/228#issuecomment-14697216
Remove trailing whitespace
Merge pull request #228 from github/tweak-basics-of-authentication-guide

Tweak basics of authentication guide