Remove unnecessary directory changing

[aprescott]

Some parts of the code do FileUtils.cd:

# site.rb

def generate
  FileUtils.cd(@source_directory)
  # ...
end

This really shouldn't happen since it changes things for the entire running process meaning you have to be aware of what Dir.pwd is or you have to cd before doing anything relative.

Instead of cd(foo), work directly off foo in any paths.

This should also negate the acceptance test hack in spec_helper:

# TODO: Stop doing FileUtils.cd at runtime to avoid the need for this.
config.before :each do
  FileUtils.cd File.expand_path(File.join(__FILE__, "..", ".."))
end

[aprescott]

Dir#chdir with a block might make this easier.