compiler: Verify version Go 1.6 strictly, tip not supported. (#461)
compiler: Verify version Go 1.6 strictly, tip not supported. (#461)

Be more strict in the version check, so it's clear which versions are supported. Only Go 1.6, 1.6.1, and 1.6.2, not older nor newer.

This should help communicate to people who try running GopherJS with tip and run into issues that it's because 1.6 strictly is required, rather than "1.6 and newer".
gopherjs/gopherjs,gopherjs/gopherjs,albrow/gopherjs,albrow/gopherjs,albrow/gopherjs,gopherjs/gopherjs,gopherjs/gopherjs,gopherjs/gopherjs