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/rsync/README.md

@@ -2,20 +2,20 @@
 
 Defines [rsync][1] aliases.
 
-macOS users are encouraged to use *rsync* from [Homebrew][2] or [MacPorts][3],
+macOS users are encouraged to use _rsync_ from [Homebrew][2] or [MacPorts][3],
 which has additional enhancements including patches from [Bombich][4].
 
 ## Aliases
 
-- `rsync-copy` copies files and directories from *source* to *destination*.
-- `rsync-move` moves files and directories from *source* to *destination*.
-- `rsync-update` updates files and directories on *destination*.
-- `rsync-synchronize` synchronizes files and directories between *source* and
-  *destination*.
+- `rsync-copy` copies files and directories from _source_ to _destination_.
+- `rsync-move` moves files and directories from _source_ to _destination_.
+- `rsync-update` updates files and directories on _destination_.
+- `rsync-synchronize` synchronizes files and directories between _source_ and
+  _destination_.
 
 ## 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][5]._
 
 - [Sorin Ionescu](https://github.com/sorin-ionescu)