Upgrade Go to 1.6.3

1.6.3 will be a security release. The prerelease announcement is here: https://groups.google.com/forum/m/#!topic/golang-announce/7JTsd70ZAT0

#18333 (moved) was the upgrade to 1.6.2.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information