Fix mutable var and warning

Author: hebertialmeida

Source/FolioReaderPage.swift

@@ -108,7 +108,7 @@ public class FolioReaderPage: UICollectionViewCell, UIWebViewDelegate, UIGesture
 
     func loadHTMLString(htmlContent: String!, baseURL: NSURL!) {
 		// Insert the stored highlights to the HTML
-		var tempHtmlContent = htmlContentWithInsertHighlights(htmlContent)
+		let tempHtmlContent = htmlContentWithInsertHighlights(htmlContent)
         // Load the html into the webview
         webView.alpha = 0
         webView.loadHTMLString(tempHtmlContent, baseURL: baseURL)