Title Line Breaks Cause Issues in JSON File (#50)

This seems related to issue #47 , but it's showing up in a different
place. Here, it seems that the line breaks are not being escaped in the
resulting lunr.json file for the search functionality.

## Suggested resolution
As the whitespace in a title (whether intentional or not) isn't really
relevant to the search functionality, simply using the same replace
function in xpath as is used elsewhere in the `data-to-json.xsl` file
seems a simple and consistent fix for this issue.

xsl/data-to-json.xsl

@@ -38,7 +38,7 @@
     <xsl:text>",</xsl:text>
 
     <xsl:text>"t": "</xsl:text>
-    <xsl:value-of select="dita-ot:escapeQuote(@title)"/>
+    <xsl:value-of select="normalize-space(dita-ot:escapeQuote(@title))"/>
     <xsl:text>",</xsl:text>
 
     <xsl:text>"k": "</xsl:text>