Update URL of article about Blogger migration
Merge pull request #1242 from Florent2/patch-1

Update URL of article about Blogger migration
Update history to reflect merge of #1242
Fix coolaj86 link to migrate from Blogger to Jekyll. Modifies #1242.
Restrict activesupport dependency to pre-4.0.0 to maintain <= 1.9.2 compatibility.
Default Markdown template parser for new sites to RedCarpet via _config.yml. Related: #1236.
Update history to reflect restriction of activesupport dependency.
Merge pull request #1245 from mojombo/jekyll-new-redcarpet

Default Markdown template parser for new sites to RedCarpet
Update history to reflect merge of #1245