Fix handling of < in values, broken by map merging

Fixes issue #24.

decode_test.go

diff --git a/decode_test.go b/decode_test.go
index d2b45b3..a290645 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -371,6 +371,12 @@
 		"a: 3s",
 		map[string]time.Duration{"a": 3 * time.Second},
 	},
+
+	// Issue #24. 
+	{
+		"a: <foo>",
+		map[string]string{"a": "<foo>"},
+	},
 }
 
 type inlineB struct {

encode_test.go

diff --git a/encode_test.go b/encode_test.go
index c7461d5..83dc490 100644
--- a/encode_test.go
+++ b/encode_test.go
@@ -219,6 +219,12 @@
 		map[string]time.Duration{"a": 3 * time.Second},
 		"a: 3s\n",
 	},
+
+	// Issue #24. 
+	{
+		map[string]string{"a": "<foo>"},
+		"a: <foo>\n",
+	},
 }
 
 func (s *S) TestMarshal(c *C) {

resolve.go

diff --git a/resolve.go b/resolve.go
index fdc4909..863c314 100644
--- a/resolve.go
+++ b/resolve.go
@@ -27,7 +27,6 @@
 		t[int(c)] = 'M' // In map
 	}
 	t[int('.')] = '.' // Float (potentially in map)
-	t[int('<')] = '<' // Merge
 
 	var resolveMapList = []struct {
 		v   interface{}