Move content/ into new contentDir content/en/

in preparation for adding new translations such as Chinese.

Paths for "readfile" shortcode are adjusted accordingly.

See #461

config.toml

@@ -271,3 +271,10 @@ anchor = "smart"
     identifier = "github"
     post = "external"
     url = "https://github.com/gohugoio/hugo"
+
+
+[languages]
+  [languages.en]
+    contentDir = "content/en"
+    languageName = "English"
+    weight = 1

content/en/content-management/formats.md

@@ -29,7 +29,7 @@ Before you begin writing your content in markdown, Blackfriday has a known issue
 
 You can configure multiple aspects of Blackfriday as show in the following list. See the docs on [Configuration][config] for the full list of explicit directions you can give to Hugo when rendering your site.
 
-{{< readfile file="/content/readfiles/bfconfig.md" markdown="true" >}}
+{{< readfile file="/content/en/readfiles/bfconfig.md" markdown="true" >}}
 
 ## Extend Markdown
 

content/en/content-management/sections.md

@@ -81,7 +81,7 @@ With the available [section variables and methods](#section-page-variables-and-m
 
 Also see [Page Variables](/variables/page/).
 
-{{< readfile file="/content/readfiles/sectionvars.md" markdown="true" >}}
+{{< readfile file="/content/en/readfiles/sectionvars.md" markdown="true" >}}
 
 ## Content Section Lists