Boost 1.67.0

[springmeyer]

Created with:

git checkout -b boost-1.67.0
./utils/new_boost.sh create 1.67.0 1.66.0
git add scripts/boost*/1.67.0/
git commit -a -m "boost 1.67.0"
./utils/new_boost.sh trigger 1.67.0

Then I noticed the boost_python builds failed. Debugging locally I found that the library name changed. Fixed this in bb564ee and then manually triggered a build for just boost_python in: https://travis-ci.org/mapbox/mason/builds/369861321 with ./mason trigger boost_libpython 1.67.0

[springmeyer]

@AllieOop - assigned you as a reviewer here. Let's go over this together to check my work / confirm the fix works before merging.

[sssoleileraaa]

My PR walk-through with @springmeyer helped make sense of the changes he made. The first commit shows the fix he made and that's what we spent time discussing. The second commit is the automated/boilerplate code.

After I run through a manual test of boost_libpython like we discussed, I think we should be good to merge this!