Fix markdown

Author: avit

UPGRADING.md

@@ -3,11 +3,11 @@
 ## 0.12.0
 
 Previous versions used `start_date` as a hash key. This version introduces a
-deprecation by renaming to `start_time` for consistency: see [issue
-#102](https://github.com/seejohnrun/ice_cube/issues/102). The old name will
-continue to be recognized when reading seralized schedules from previous
-versions, and we will default to exporting serialized schedules
-with *both* names. You can disable this duplication by setting
-`IceCube.compatibility = 12` after your downstream code is updated to look for
-`start_time`. Watch for deprecation notices in your log.
+deprecation by renaming to `start_time` for consistency: see 
+[issue #102][issue-102]. The old name will continue to be recognized when
+reading seralized schedules from previous versions, and we will default to
+exporting serialized schedules with *both* names. You can disable this
+duplication by setting `IceCube.compatibility = 12` after your downstream code
+is updated to look for `start_time`. Watch for deprecation notices in your log.
 
+[issue-102]: https://github.com/seejohnrun/ice_cube/issues/102