Merge pull request #28 from radeksimko/go-mod

Enable go modules

go.mod

@@ -0,0 +1,3 @@
+module github.com/mattn/go-isatty
+
+require golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223 h1:DH4skfRX4EBpamg7iV4ZlCpblAHI6s6TDM39bFZumv8=
+golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=