Begin expanding upon the environment functionality with per-env config files.

The currently extant environment functionality doesn't really afford one much in terms of capabilities -- this is a first step towards making it useful.

Key use-case for me is that I want the hostname to be different in development, staging, and production. (Workstation, Github Pages, and DreamHost or some other such system respectively...)
Add/correct method documentation.
Merge branch 'expand_environment_functionality_take3' into integration

Conflicts:
	lib/octopress.rb
	lib/octopress/configuration.rb
	lib/octopress/inquirable_string.rb
	lib/spec/octopress/configuration_spec.rb
	lib/spec/octopress/octopress_spec.rb
Merge branch 'documentation_enhancements' into integration

Conflicts:
	lib/octopress.rb