Fixes #35: Retrieve dotted keys

toml.go

diff --git a/toml.go b/toml.go
index 2896da7..bf35cd3 100644
--- a/toml.go
+++ b/toml.go
@@ -65,7 +65,11 @@
 	if key == "" {
 		return t
 	}
-	return t.GetPath(strings.Split(key, "."))
+	comps, err := parseKey(key)
+	if err != nil {
+		return nil
+	}
+	return t.GetPath(comps)
 }
 
 // GetPath returns the element in the tree indicated by 'keys'.