Improve README.md and code coverage a bit.

That said, Ctrl-C handling isn't unit tested but known to work.

README.md

@@ -12,19 +12,19 @@ When set, it is expected the process to abort any on-going execution early.
 
 The signal can be read via two ways:
 
-  select {
-  case <- interrupt.Channel:
-    // Handle abort.
-  case ...
-    ...
-  default:
-  }
+    select {
+    case <- interrupt.Channel:
+      // Handle abort.
+    case ...
+      ...
+    default:
+    }
 
 or
 
-  if interrupt.IsSet() {
-    // Handle abort.
-  }
+    if interrupt.IsSet() {
+      // Handle abort.
+    }
 
 [![GoDoc](https://godoc.org/github.com/maruel/interrupt?status.svg)](https://godoc.org/github.com/maruel/interrupt)
 [![Build Status](https://travis-ci.org/maruel/interrupt.svg?branch=master)](https://travis-ci.org/maruel/interrupt)

interrupt_test.go

@@ -18,12 +18,21 @@ func TestSet(t *testing.T) {
 	default:
 	}
 
+	HandleCtrlC()
+
+	ut.AssertEqual(t, false, IsSet())
+	select {
+	case <-Channel:
+		t.Fatal()
+	default:
+	}
+
 	Set()
-	ut.AssertEqual(t, true, IsSet())
-	i, ok := <-Channel
-	ut.AssertEqual(t, true, i)
-	ut.AssertEqual(t, true, ok)
-	i, ok = <-Channel
-	ut.AssertEqual(t, true, i)
-	ut.AssertEqual(t, true, ok)
+
+	for i := 0; i < 2; i++ {
+		ut.AssertEqual(t, true, IsSet())
+		x, ok := <-Channel
+		ut.AssertEqual(t, true, x)
+		ut.AssertEqual(t, true, ok)
+	}
 }