Upgrade to latest llvm + mason

[springmeyer]

There is a newer, stable llvm series out (mapbox/mason#452). Not urgent, but also no reason not to upgrade from 4.0.0 to 4.0.1 in the future:

diff --git a/scripts/setup.sh b/scripts/setup.sh
index 6b9d327..cb41656 100755
--- a/scripts/setup.sh
+++ b/scripts/setup.sh
@@ -3,8 +3,8 @@
 set -eu
 set -o pipefail
 
-export MASON_RELEASE="${MASON_RELEASE:-v0.9.0}"
-export MASON_LLVM_RELEASE="${MASON_LLVM_RELEASE:-4.0.0}"
+export MASON_RELEASE="${MASON_RELEASE:-v0.14.1}"
+export MASON_LLVM_RELEASE="${MASON_LLVM_RELEASE:-4.0.1}"
 
 PLATFORM=$(uname | tr A-Z a-z)
 if [[ ${PLATFORM} == 'darwin' ]]; then

However, oddly I can't find any llvm 4.0.1 specific release notes yet, only found http://releases.llvm.org/4.0.1/docs/ReleaseNotes.html which look identical to http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html