Refined verbose output.

Previously, tests were always run in verbose mode. With this change, when a
group of tests runs, verbose mode is off.
Added SVNx::IO::Element.

This class represents Subversion as a File- or Pathname-like object, instead of
as a command line.
Added test and implementation of exists? method.
Added test and implementation of directory? method.
Added test and implementation of get_info method.
Added test of get_info method when file not in svn.
Added test/implementation of in_svn? method.
Refined get_info to return nil on element not in svn.
Added find_ for modified entries remotely and locally.

This change adds find_in_log and find_by_status, which get modified elements via
"svn log" and "svn st". This is not complete, since Status and Log entries
should be the same.
Integrated Action class.

Further integrated Action into Entry classes.
Integrated root path into Status entry.

This is necessary for Log and Status entries appearing the same, with a full
path, and a name relative to its location within Svn.
Refined Action class to be more like a set of constants.

Actions are more like constants (they have no state), so this change revises
them to be constants.
Action constructor now returns nil for an invalid action type.
Refined Action class to be a set of constants.
Expanded methods to find matching element paths.

This change adds functionality to get the list of paths that changed in the
current status, or in the log.
Refactored tests.
Changed Status and Log entries to be sorted.

Previously those entries were returned in the order of Svn, which is not sorted.
With this change, entries are always sorted by name.
Added cat method to Element.

This method does the same as "svn cat".
Added <=> and to_s methods, from PVN.