Add smartDashes flag for Blackfriday

To allow the end users to disable any form of smart dashes
(LaTeX-style or not) while keeping the rest of Blackfriday
SmartyPants features.

Depends on https://github.com/russross/blackfriday/pull/190
"Add HTML_SMARTYPANTS_DASHES for toggling smart dashes"
to be accepted by Blackfriday developers.

helpers/content.go

@@ -45,6 +45,7 @@ type Blackfriday struct {
 	AngledQuotes    bool
 	Fractions       bool
 	HrefTargetBlank bool
+	SmartDashes     bool
 	LatexDashes     bool
 	PlainIDAnchors  bool
 	Extensions      []string
@@ -58,6 +59,7 @@ func NewBlackfriday() *Blackfriday {
 		AngledQuotes:    false,
 		Fractions:       true,
 		HrefTargetBlank: false,
+		SmartDashes:     true,
 		LatexDashes:     true,
 		PlainIDAnchors:  false,
 	}
@@ -169,6 +171,10 @@ func GetHTMLRenderer(defaultFlags int, ctx *RenderingContext) blackfriday.Render
 		htmlFlags |= blackfriday.HTML_HREF_TARGET_BLANK
 	}
 
+	if ctx.getConfig().SmartDashes {
+		htmlFlags |= blackfriday.HTML_SMARTYPANTS_DASHES
+	}
+
 	if ctx.getConfig().LatexDashes {
 		htmlFlags |= blackfriday.HTML_SMARTYPANTS_LATEX_DASHES
 	}