Do not require source-highlight

source-highlight is not necessary (-s|--src will fall back to plain text
if it's missing) and requiring it strictly breaks RHEL6 build.

deb users can follow Suggests field; rpm users will have to find out about
it and install it separately.  (Optional requires do exist in newer RPM,
but it's not worth the effort/ifdef bloat.)

packaging/debian/control

 Package: __MKIT_PROJ_PKGNAME__
 Architecture: all
 Depends:
- source-highlight,
  perl,
  procps,
+Suggests:
+ source-highlight,
 Description: __MKIT_PROJ_NAME__ - __MKIT_PROJ_TAGLINE__
  Shellfu is an attempt to add modularity to your shell scripts.
  .

packaging/template.spec

 BuildRequires:  %{pspkg}
 
 Requires: %{pspkg}
-Requires: source-highlight
 %description
 Shellfu is an attempt to add modularity to your shell scripts.