refactors Cli::Publish to obtain master middleman

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Uses a non-local master_middleman if specified

Cli::Publish obtains master_middleman_dir from config and local_repo_dir

Configuration respects #layout_repo

[#68836194]

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Documentation update for layout_repo config option.

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Factors MasterMiddleman#path out of Cli::Publish

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Bump bookbinder version to 0.2.1

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>