README: replace "golang" moniker with "Go"
README: replace "golang" moniker with "Go"

This commit replaces the "golang" moniker in the README file with the
appropriate name of "Go" per https://golang.org/doc/faq#go_or_golang.

In this context, no disambiguation is required.
alk/gperftools,gperftools/gperftools,gperftools/gperftools,gperftools/gperftools,alk/gperftools,gperftools/gperftools,alk/gperftools,alk/gperftools