Add command line options

* -c:
  Source <file> prior to other configuration files
* -d:
  Enable debug mode
* -v:
  Enable verbose mode
Refer users of `git submodule` to v1.7.12 or later

See commits

* be8779f7ac9a3be9aa783df008d59082f4054f67
* 95e7705310bce3b2721ebf789776c170cf424abb

in git's git repository
Support more configuration files

Supported files

* /etc/vcsh/config
* $XDG_CONFIG_HOME/vcsh/config
* vcsh -c <file>
Improve wording in manpage
Correct a few missing words in help
Merge pull request #31 from mek-apelsin/master

Fix mistake and improve wording in help()

Was: "Help isn't showing correct number of <repo>"
Fix option parsing

Previously, only -d would shift parameters from the option stack
correctly.
Escape underscores in doc/error_codes.md
Apply patch by Ian Campbell

See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=699093 for details
Release 1.0.1
Typo in warning message 'DETROY' -> 'DESTROY'.
Use rm -f when removing a git repo.

Git repos place the files as write-protected by default, so the
vcsh delete operation requires the user to typo 'y' repeatedly as the
repo is deleted. Using -f removes the repository properly.
Merge branch 'destroy-typo' of https://github.com/jsternberg/vcsh
Merge branch 'force-delete-repo' of https://github.com/jsternberg/vcsh
Merge branch 'debbug-699093'
Release 1.1
Merge branch 'master' into debian