Updated README for 0.6.4 release

README.md

@@ -17,7 +17,9 @@ by [Leonidas Poulopoulos (@leopoul)](http://ncclient.org) and Einar Nilsen-Nygaa
 
 |  Date  | Release | Description |
 | :----: | :-----: | :---------- |
-| 08/20/18 | `0.6.2` | Migration to user `selectors` instead of `select`, allowing higher scale operations; improved `netconf:base:1.1` parsing. |
+| 04/07/19 | `0.6.4` | See [release page](https://github.com/ncclient/ncclient/releases/tag/v0.6.4) |
+| 09/26/18 | `0.6.3` | See [release page](https://github.com/ncclient/ncclient/releases/tag/v0.6.3) |
+| 08/20/18 | `0.6.2` | See [release page](https://github.com/ncclient/ncclient/releases/tag/v0.6.2) |
 | 07/02/18 | `0.6.0` | Minor release reinstating Python 3.7 and greater compatibility, but necessitating a change to client code that uses `async_mode`. |
 | 07/02/18 | `0.5.4` | New release rolling up myriad of small commits since `0.5.3`. Please note that this release is **incompatible wth Python 3.7** due to the use of a new Python 3.7 keyword, `async`, in function signatures. This will be resolved in 0.6.0|
 
@@ -179,6 +181,8 @@ Thus, making a release becomes a simple process:
 
 ## Contributors
 
+* v0.6.4: @davidhankins, @mzagozen, @knobix, @markafarrell, @psikala, @moepman, @apt-itude, @yuekyang
+* v0.6.3: @rdkls, @Anthony25, @rsmekala, @vnitinv, @siming85
 * v0.6.2: @einarnn, @glennmatthews, @bryan-stripe, @nickylba
 * v0.6.0: @einarnn
 * v0.5.4: @adamcubel, Joel Teichroeb, @leopoul, Chase Garner, @budhadityabanerjee, @earies, @ganeshrn, @vnitinv, Siming Yuan, @mirceaaulinic, @stacywsmith, Xavier Hardy, @jwwilcox, @QijunPan, @avangel, @marekgr, @hugovk, @felixonmars, @dexteradeus