Uses the SVN::Client manpage to obtain files from a subversion repository
for inclusion in a distribution made with the Dist::Zilla manpage.

'[SvnObtain]' sections in your _dist.ini_ file describe a set of Subversion
repositories that will be downloaded into the current directory prior to
building a distribution. Subdirectories will be created that correspond to
the name of the projects listed in that section. Optionally, after the URL
of the subversion repository, you may specify a particular revision to
check out. If you do not specify a revision, 'HEAD' will be used. For
instance, to include a copy MIT's simile timeline widget into your
distribution, your _dist.ini_ would contain something like this:

[SvnObtain]
simile = http://simile-widgets.googlecode.com/svn