Fixed broken logic figuring out tags from make files.

 	modified:   drushsubtree.drush.inc
Added implementation of hook_buildmanager_parse_error_output().

  And added improved handline of error output.

 	modified:   drushsubtree.drush.inc
Added improved error handling.

  Checks to make sure tags/versions specified in make file correspond with tags
  available at remote.

 	modified:   drushsubtree.drush.inc
Updated SHA1 output to terminal to make it easier to read.

 	modified:   drushsubtree.subtreecommander.class.inc
Added subtree-show-subtrees command.

	modified:   drushsubtree.drush.inc
Updated error handing in subtree add.

  Minor update. Just tidying up code and comments.

	modified:   drushsubtree.drush.inc
Added subtree-get-info command.
Updated help message.
 	modified:   drushsubtree.subtreecommander.class.inc
Added handling for annotated tags.

	modified:   drushsubtree.drush.inc
Fixed tag check. (Added missing option.)

	modified:   drushsubtree.drush.inc
Added subtree-get-head / subtree-split command.

  Returns commit ID (and tag if available) for HEAD of subtree project
  requested.

	modified:   drushsubtree.drush.inc
	modified:   drushsubtree.subtreecommander.class.inc
Fixed broken check for library projects.

	modified:   drushsubtree.drush.inc
Fixed syntax error.

	modified:   drushsubtree.drush.inc
Changed error to warning, when subtree not included in make.

	modified:   drushsubtree.drush.inc
Minor updates to propmt language.

	modified:   drushsubtree.drush.inc
Added subtree-get-remote-head command.

	modified:   drushsubtree.drush.inc
	modified:   drushsubtree.gitcommander.class.inc
Update method names. Use camel case.

	modified:   drushsubtree.drush.inc
	modified:   drushsubtree.gitcommander.class.inc
Updated subtree-get-tags, generate command with GitCommander.

	modified:   drushsubtree.drush.inc
Updated command name and aliases.

  This groups subtree-get-head and subtree-get-head-remote together when user
  sees list of commands with drush --filter=drushsubtree.

	modified:   drushsubtree.drush.inc
Added drush subtree-compare-heads.

	modified:   drushsubtree.drush.inc