Add support for markdown to HTML conversion (matrix). Closes #663 (#670)

This uses our own gomatrix lib with the SendHTML function which
adds HTML to formatted_body in matrix.
golang-commonmark is used to convert markdown into valid HTML.

bridge/matrix/matrix.go

@@ -3,6 +3,7 @@ package bmatrix
 import (
 	"bytes"
 	"fmt"
+	"html"
 	"mime"
 	"regexp"
 	"strings"
@@ -112,8 +113,8 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 	// Edit message if we have an ID
 	// matrix has no editing support
 
-	// Post normal message
-	resp, err := b.mc.SendText(channel, msg.Username+msg.Text)
+	// Post normal message with HTML support (eg riot.im)
+	resp, err := b.mc.SendHTML(channel, msg.Text, html.EscapeString(msg.Username)+helper.ParseMarkdown(msg.Text))
 	if err != nil {
 		return "", err
 	}