Fix marshaler typos (#927)

Author: pelletier

marshaler.go

@@ -92,7 +92,7 @@ func (enc *Encoder) SetIndentTables(indent bool) *Encoder {
 // SetMarshalJsonNumbers forces the encoder to serialize `json.Number` as a
 // float or integer instead of relying on TextMarshaler to emit a string.
 //
-// *Unstable:* This method does not follow the compatiblity guarnatees of
+// *Unstable:* This method does not follow the compatibility guarantees of
 // semver. It can be changed or removed without a new major version being
 // issued.
 func (enc *Encoder) SetMarshalJsonNumbers(indent bool) *Encoder {