make selection of features/fixes for announcement

docs/announce/2015.07.md

@@ -16,7 +16,14 @@ Prague, new home to one of the Rakudo core developers.
 
 Some of the changes in this release are outlined below:
 
-* tbd
+* Cool.substr(-rw) and &substr(-rw) now also accept a Range
+* Added trait "is required" on class attributes (and "!" sugar)
+* $?ROUTINE and $?BLOCK
+* &words implemented (to completement .words)
+* Numeric conversion ops (== > etc) for DateTimes
+* samewith() now also works in subs
+* Calling the .clone method with alternate values, no longer changes original
+* .grep and &grep now consumes multiple elements for many-param blocks
 
 These are only some of the changes in this release. For a more
 detailed list, see "docs/ChangeLog".