Don't print `Running` for commands that aren't run

Also print the commands only right before they're actually run.

Closes #215
Update "Contributing to the Docs"
auto merge of #555 : alexcrichton/cargo/issue-215, r=brson

Also print the commands only right before they're actually run.

Closes #215
Center main content in Safari
auto merge of #567 : EduardoBautista/cargo/fix-centering-on-safari, r=alexcrichton

The website is not centered in Safari.
Fix `make dist` and distcheck breakage

Fixes a regression from #559.
auto merge of #568 : mbrubeck/cargo/dist-fix, r=alexcrichton

Fixes a regression from #559.
auto merge of #564 : EduardoBautista/cargo/contributing-to-docs, r=alexcrichton

The docs are now in the main cargo repository.
Fix list_files_git for paths in subdirs of a repo

list_files_git previously assumed that the package was always at the root of
the git repository.  This broke when trying to list files for a package in a
subdirectory of a repo, or in other cases, e.g. if the user's home directory
is a git repo.