Add hooks for setup()

* Fix and expand manpage
* Use explicit variable names in hook()

Thanks to Vincent Demeester for this idea.

One to go and that may just move to github issues...

Thanks to David Bremner for reporting this

* Refer to README.md
* Add note about config file being a potential security issue

* configuration is in $XDG_CONFIG_HOME/vcsh/config
* $VCSH_GITIGNORE can be set to 'exact' or 'recursive'

People arriving via http://onethingwell.org/post/14218384411/vcsh
should be able to find us..

1.7.7 is happy without parameters, 1.7.0.8 needs origin master

Conflicts:
	vcsh

* manpage
* set $VCSH_REPO_NAME (this assumes .git suffix!)

Conflicts:
	doc/error_codes.md