bump roadmap dates

docs/docsite/rst/roadmap/ROADMAP_2_8.rst

@@ -13,17 +13,17 @@ Expected
 
 PRs must be raised well in advance of the dates below to have a chance of being included in this Ansible release.
 
-- 2019-03-28 Alpha 1 **Core freeze**
+- 2019-04-04 Alpha 1 **Core freeze**
   No new features to ``support:core`` code.
   Includes no new options to existing Core modules
 
-- 2019-04-04 Beta 1 **Feature freeze**
+- 2019-04-11 Beta 1 **Feature freeze**
   No new functionality (including modules/plugins) to any code
 
-- 2019-04-18 Release Candidate 1
-- 2019-04-25 Release Candidate 2 (if needed)
-- 2019-05-02 Release Candidate 3 (if needed)
-- 2019-05-09 Release
+- 2019-04-25 Release Candidate 1
+- 2019-05-02 Release Candidate 2 (if needed)
+- 2019-05-09 Release Candidate 3 (if needed)
+- 2019-05-16 Release