Description of problem:
using /bin/ronn $_file to build a manpage from mark-down without having groff-base installed will fail.


Version-Release number of selected component:
0.7.3 (rubygem-ronn-0.7.3-3.fc19.noarch)


How reproducible:
always when groff-base is not installed or pulled-in through otherwise needed dependency, e.g. during mock or koji-build


Steps to Reproduce:
1. create spec-file with `BuildRequires: rubygem-ronn`
   don't have `BuildRequires: groff-base`
   convert mark-down to manpage invoking /bin/ronn ${_file} during %build
2. build package with mock or koji-build
3. have a look inside {build,root}.log

Actual results:
groff-base will not get installed as required and build.log shows like:

     roff: ./${_file}.1
  sh: groff: command not found
     html: ./${_file}.1.html                                    +man


Expected results:
/bin/ronn should create manpage properly.


Proposed solution:
groff-base should get installed through dependency, since it is needed during `/bin/ronn`-invocation. rubygem-ronn should have Requires: groff-base


Additional info (see {build,root}.log):
without groff-base: https://koji.fedoraproject.org/koji/taskinfo?taskID=5463867
with groff-base:    https://koji.fedoraproject.org/koji/taskinfo?taskID=5463901