Apply suggestions from @dlongley code review

Co-Authored-By: Dave Longley <dlongley@digitalbazaar.com>

Author: gkellogg

lib/documentLoaders/node.js

@@ -67,7 +67,7 @@ module.exports = ({
     // add any optional requestProfile
     if(options.requestProfile) {
       headers.Accept =
-        headers.Accept + ", application/ld+json;profile=${options.requestProfile}";
+        headers.Accept + `, application/ld+json;profile=${options.requestProfile}`;
     }
 
     let result;

lib/documentLoaders/xhr.js

@@ -51,7 +51,7 @@ module.exports = ({
     // add any optional requestProfile
     if(options.requestProfile) {
       headers.Accept =
-        headers.Accept + ", application/ld+json;profile=${options.requestProfile}";
+        headers.Accept + `, application/ld+json;profile=${options.requestProfile}`;
     }
 
     let req;

lib/jsonld.js

@@ -857,7 +857,7 @@ jsonld.documentLoader = async url => {
  * @param url the URL to fetch.
  * @param [options] the options to use:
  *          [documentLoader] the document loader to use.
- *          [extractAllScripts] concatenates all matching script elements..
+ *          [extractAllScripts] concatenates all matching script elements.
  *          [profile] used when selecting from HTML script elements.
  *          [requestProfile] one or more profile IRIs to use in the request.
  *
@@ -920,7 +920,7 @@ jsonld.get = async function(url, options) {
         }
         if(frag && remoteDoc.document.length === 0) {
           throw new JsonLdError(
-            'No script tag found with id=${frag}.',
+            `No script tag found with id=${frag}.`,
             'jsonld.InvalidScriptElement', {
               code: 'invalid script element',
               remoteDoc