general: Update documentation better qualifying runcom paths

Zsh and Prezto files don't always reside in `~/`. Instead, they have
a more spec compliant location (`${ZDOTDIR:-$HOME}/`). Make them
unambiguous in the documentation. Likewise, for `$GNUPGHOME`.

Further, add instruction for optionally setting up Prezto in
`$XDG_CONFIG_HOME`.

While at this, also add clarification on relative ordering of some of
the modules, apply more formatting tweaks and doc improvements.

modules/fasd/README.md

@@ -2,11 +2,11 @@
 
 [Fasd][1] is a command-line productivity booster, inspired by tools like
 [autojump][2], [z][3] and [v][4], it offers quick access to files and
-directories by keeping track of files and directories  that were previously
+directories by keeping track of files and directories that were previously
 accessed.
 
-For completion to work, this module must be loaded **after** the *completion*
-module.
+For shell completion to work, this module must be loaded _after_ the
+[_`completion`_][5] module.
 
 The Prezto Fasd configuration differs from the default. The default aliases have
 been disabled.
@@ -23,12 +23,12 @@ instead of the bundled version.
 
 ## Completion
 
-Type `,`, `f,`, `d,` in front of a comma-separated query or type `,,`,  `,,f`,
+Type `,`, `f,`, `d,` in front of a comma-separated query or type `,,`, `,,f`,
 `,,d` at the end of a comma-separated query then hit <kbd>TAB</kbd>.
 
 ## Authors
 
-*The authors of this module should be contacted via the [issue tracker][5].*
+_The authors of this module should be contacted via the [issue tracker][6]._
 
 - [Wei Dai](https://github.com/clvv)
 - [Sorin Ionescu](https://github.com/sorin-ionescu)
@@ -37,4 +37,5 @@ Type `,`, `f,`, `d,` in front of a comma-separated query or type `,,`,  `,,f`,
 [2]: https://github.com/joelthelion/autojump
 [3]: https://github.com/rupa/z
 [4]: https://github.com/rupa/v
-[5]: https://github.com/sorin-ionescu/prezto/issues
+[5]: ../completion#readme
+[6]: https://github.com/sorin-ionescu/prezto/issues