Move git and url checks into pkg

This moves the IsGIT and IsURL functions out of the generic `utils`
package and into their own `urlutil` pkg.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

urlutil/url.go

@@ -0,0 +1,19 @@
+package urlutil
+
+import "strings"
+
+var validUrlPrefixes = []string{
+	"http://",
+	"https://",
+}
+
+// IsURL returns true if the provided str is a valid URL by doing
+// a simple change for the transport of the url.
+func IsURL(str string) bool {
+	for _, prefix := range validUrlPrefixes {
+		if strings.HasPrefix(str, prefix) {
+			return true
+		}
+	}
+	return false
+}