Add dates to RELEASES.md

Author: cuviper

RELEASES.md

@@ -1,16 +1,16 @@
-# Release 0.2.2
+# Release 0.2.2 (2018-05-22)
 
 - [Updated dependencies][14].
 
 [14]: https://github.com/rust-num/num-derive/pull/14
 
-# Release 0.2.1
+# Release 0.2.1 (2018-05-09)
 
 - [Updated dependencies][12] -- thanks @spearman!
 
 [12]: https://github.com/rust-num/num-derive/pull/12
 
-# Release 0.2.0
+# Release 0.2.0 (2018-02-21)
 
 - [Discriminant matching is now simplified][10], casting values directly by
   name, rather than trying to compute offsets from known values manually.
@@ -22,23 +22,23 @@
 [11]: https://github.com/rust-num/num-derive/pull/11
 
 
-# Release 0.1.44
+# Release 0.1.44 (2018-01-26)
 
 - [The derived code now explicitly allows `unused_qualifications`][9], so users
   that globally deny that lint don't encounter an error.
 
 [9]: https://github.com/rust-num/num-derive/pull/9
 
 
-# Release 0.1.43
+# Release 0.1.43 (2018-01-23)
 
 - [The derived code now explicitly allows `trivial_numeric_casts`][7], so users
   that globally deny that lint don't encounter an error.
 
 [7]: https://github.com/rust-num/num-derive/pull/7
 
 
-# Release 0.1.42
+# Release 0.1.42 (2018-01-22)
 
 - [num-derive now has its own source repository][num-356] at [rust-num/num-derive][home].
 - [The derivation macros have been updated][3] to using `syn` 0.12.  Support for complex