Dedent the changelog entries in the posts.

_posts/2014-10-02-diffoscope-3-released.md

_posts/2014-11-09-diffoscope-4-released.md

_posts/2014-12-30-diffoscope-5-released.md

_posts/2015-01-07-diffoscope-6-released.md

_posts/2015-01-10-diffoscope-7-released.md

_posts/2015-02-10-diffoscope-8-released.md

_posts/2015-02-15-diffoscope-9-released.md

_posts/2015-03-20-diffoscope-10-released.md

_posts/2015-03-23-diffoscope-11-released.md

_posts/2015-03-27-diffoscope-12-released.md

_posts/2015-03-28-diffoscope-13-released.md

_posts/2015-04-02-diffoscope-14-released.md

_posts/2015-04-04-diffoscope-15-released.md

_posts/2015-04-16-diffoscope-16-released.md

_posts/2015-04-30-diffoscope-17-released.md

_posts/2015-05-09-diffoscope-18-released.md

_posts/2015-05-12-diffoscope-19-released.md

_posts/2015-05-17-diffoscope-20-released.md

_posts/2015-06-13-diffoscope-21-released.md

_posts/2015-06-14-diffoscope-22-released.md