Update lifecycle schedule

Author: meshcollider

_includes/posts/maintenance-table.md

@@ -5,6 +5,8 @@
 | 0.12 | 2016-02-23 | 2017-03-31  | 2018-02-28 |
 | 0.13 | 2016-08-23 | 2017-09-15  | 2018-08-01 |
 | 0.14 | 2017-03-08 | 2018-02-26  | 2019-02-01 |
-| 0.15 | 2017-09-15 | after v0.17 | TBA        |
+| 0.15 | 2017-09-15 | 2018-10-03  | 2019-08-01 |
 | 0.16 | 2018-02-26 | after v0.18 | TBA        |
-| 0.17 | TBA*       | after v0.19 | TBA        |
+| 0.17 | 2018-10-03 | after v0.19 | TBA        |
+| 0.18 | TBA*       | after v0.20 | TBA        |
+| 0.19 | TBA*       | after v0.21 | TBA        |