Replace pagedown by markdown-it

Gemfile

Gemfile.lock

app/assets/javascripts/app/helpers/handlebars-helpers.js

app/assets/javascripts/app/helpers/text_formatter.js

app/assets/javascripts/app/pages/single-post-viewer.js

app/assets/javascripts/app/views/comment_view.js

app/assets/javascripts/app/views/content_view.js

app/assets/javascripts/app/views/post_view.js

.../app/views/single-post-viewer/single_post_content_view.js

app/assets/javascripts/main.js

config/locales/diaspora/en.yml

features/desktop/signs_up.feature

lib/assets/javascripts/markdown-it-diaspora-linkify.js

lib/assets/javascripts/posix-bracket-expressions.js

spec/javascripts/app/helpers/text_formatter_spec.js

vendor/assets/javascripts/markdown.js

vendor/assets/javascripts/markdown/Markdown.Converter.js

vendor/assets/javascripts/markdown/Markdown.Sanitizer.js