Implemented negative numbers

src/build/token/Tokenize_test.go

@@ -166,6 +166,19 @@ func TestNegateAfterOperator(t *testing.T) {
 	}
 }
 
+func TestNegateNumber(t *testing.T) {
+	tokens := token.Tokenize([]byte(`-1`))
+
+	expected := []token.Kind{
+		token.Number,
+		token.EOF,
+	}
+
+	for i, kind := range expected {
+		assert.Equal(t, tokens[i].Kind, kind)
+	}
+}
+
 func TestOperatorAssign(t *testing.T) {
 	tokens := token.Tokenize([]byte(`a += b -= c *= d /= e &= f |= g ^= h <<= i >>= j`))