feat(plan): add support for pretest and release candidate builds

Add support for naming release and builds accordingly when given a git
ref for a pretest (90 or above patch number) or release
candidate ("-rcX" at the end of the tag).

pkg/sanitize/string.go

@@ -0,0 +1,9 @@
+package sanitize
+
+import "regexp"
+
+var nonAlphaNum = regexp.MustCompile(`[^\w_-]+`)
+
+func String(s string) string {
+	return nonAlphaNum.ReplaceAllString(s, "-")
+}