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

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

Closes #215
Allows bootstrapping win64 from win32 snapshot.
Remove triple = 'i686-pc-mingw32' once win64 snapshot is made.

Signed-off-by: Peter Atashian <retep998@gmail.com>
Merge commit '314d47749a79d0382eea1b710456b038a1ac84c0' into win64
Switch the URL from which nightlies are downloaded
auto merge of #562 : alexcrichton/cargo/win64, r=alexcrichton
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 bug in list_file_walk when cwd != path

Previously this was calling .is_file() on a relative path.  This would fail if
the path was not relative to the current working directory, for example when
fingerprinting a path dependency.
Test for build command fingerprints in path deps

This tests the fix for list_files_walk from #561.
Fix tests on Mac builders

Comparing URIs in /tmp was failing because of symlinks.