Rewrite markdown rendering to blackfriday v2 and rewrite orgmode rendering to go-org (#8560)

* Rewrite markdown rendering to blackfriday v2.0

* Fix style

* Fix go mod with golang 1.13

* Fix blackfriday v2 import

* Inital orgmode renderer migration to go-org

* Vendor go-org dependency

* Ignore errors :/

* Update go-org to latest version

* Update test

* Fix go-org test

* Remove unneeded code

* Fix comments

* Fix markdown test

* Fix blackfriday regression rendering HTML block

vendor/github.com/shurcooL/sanitized_anchor_name/.travis.yml

@@ -1,11 +1,11 @@
 sudo: false
 language: go
 go:
-  - 1.7
-  - tip
+  - 1.x
+  - master
 matrix:
   allow_failures:
-    - go: tip
+    - go: master
   fast_finish: true
 install:
   - # Do nothing. This is needed to prevent default install action "go get -t -v ./..." from happening here (we want it to happen inside script step).