Fix String() comment (#79)

tomltree_conversions.go

diff --git a/tomltree_conversions.go b/tomltree_conversions.go
index 21fb4d5..6a821d5 100644
--- a/tomltree_conversions.go
+++ b/tomltree_conversions.go
@@ -113,7 +113,7 @@
 	return t.String()
 }
 
-// ToString generates a human-readable representation of the current tree.
+// String generates a human-readable representation of the current tree.
 // Output spans multiple lines, and is suitable for ingest by a TOML parser
 func (t *TomlTree) String() string {
 	return t.toToml("", "")