Use new sync Map in Go 1.9

[jcscottiii]

Previously, we created maps with a manually maintained mutex:
Example here:

compliance-masonry/lib/standards.go

Lines 11 to 14 in 40b7371

	type standardsMap struct {
	mapping map[string]common.Standard
	sync.RWMutex
	}

(there's more cases throughout the code too)

Now, with Go 1.9, there's a map that's safe for concurrent access:
https://golang.org/doc/go1.9#sync-map

[jcscottiii]

Should do #262 first