Use 90. prefix for back-matter.md

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Use 90. prefix for back-matter.md

Merges #222
Closes manubot/manubot#106

Enables creating two-digit prefixed content markdown files that
will sort to come after back-matter. While back matter is intended
to be the final markdown file, some users may want to place content
after it.

manuscript.html

@@ -6,7 +6,7 @@
   <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
   <meta name="author" content="John Doe" />
   <meta name="author" content="Jane Roe" />
-  <meta name="dcterms.date" content="2019-05-14" />
+  <meta name="dcterms.date" content="2019-05-17" />
   <meta name="keywords" content="markdown, publishing, manubot" />
   <title>Manuscript Title</title>
   <style>
@@ -86,7 +86,7 @@
 <header id="title-block-header">
 <h1 class="title">Manuscript Title</h1>
 </header>
-<p><small><em> This manuscript (<a href="https://manubot.github.io/rootstock/v/5da1d32778f1ed1aa6fdc64b9614acadc7103bf3/">permalink</a>) was automatically generated from <a href="https://github.com/manubot/rootstock/tree/5da1d32778f1ed1aa6fdc64b9614acadc7103bf3">manubot/rootstock@5da1d32</a> on May 14, 2019. </em></small></p>
+<p><small><em> This manuscript (<a href="https://manubot.github.io/rootstock/v/dcb3cc43880694acf4ea25774fabe328f20c3adb/">permalink</a>) was automatically generated from <a href="https://github.com/manubot/rootstock/tree/dcb3cc43880694acf4ea25774fabe328f20c3adb">manubot/rootstock@dcb3cc4</a> on May 17, 2019. </em></small></p>
 <h2 id="authors">Authors</h2>
 <ul>
 <li><p><strong>John Doe</strong><br> <img src="images/orcid.svg" alt="ORCID icon" class="inline_icon" /> <a href="https://orcid.org/XXXX-XXXX-XXXX-XXXX">XXXX-XXXX-XXXX-XXXX</a> · <img src="images/github.svg" alt="GitHub icon" class="inline_icon" /> <a href="https://github.com/johndoe">johndoe</a> · <img src="images/twitter.svg" alt="Twitter icon" class="inline_icon" /> <a href="https://twitter.com/johndoe">johndoe</a><br> <small> Department of Something, University of Whatever · Funded by Grant XXXXXXXX </small></p></li>

manuscript.md

@@ -2,7 +2,7 @@
 author-meta:
 - John Doe
 - Jane Roe
-date-meta: '2019-05-14'
+date-meta: '2019-05-17'
 keywords:
 - markdown
 - publishing
@@ -18,10 +18,10 @@ title: Manuscript Title
 
 <small><em>
 This manuscript
-([permalink](https://manubot.github.io/rootstock/v/5da1d32778f1ed1aa6fdc64b9614acadc7103bf3/))
+([permalink](https://manubot.github.io/rootstock/v/dcb3cc43880694acf4ea25774fabe328f20c3adb/))
 was automatically generated
-from [manubot/rootstock@5da1d32](https://github.com/manubot/rootstock/tree/5da1d32778f1ed1aa6fdc64b9614acadc7103bf3)
-on May 14, 2019.
+from [manubot/rootstock@dcb3cc4](https://github.com/manubot/rootstock/tree/dcb3cc43880694acf4ea25774fabe328f20c3adb)
+on May 17, 2019.
 </em></small>
 
 ## Authors

references.json

@@ -230,13 +230,13 @@
     "title": "Open access",
     "collection-title": "MIT Press essential knowledge series",
     "publisher": "MIT Press",
-    "publisher-place": "Cambridge, Mass.",
+    "publisher-place": "Cambridge, Mass",
     "number-of-pages": "242",
-    "source": "Gemeinsamer Bibliotheksverbund ISBN",
-    "event-place": "Cambridge, Mass.",
+    "source": "Library of Congress ISBN",
+    "event-place": "Cambridge, Mass",
     "ISBN": "9780262517638",
-    "note": "OCLC: 808665987",
-    "language": "eng",
+    "call-number": "Z286.O63 S83 2012",
+    "note": "OCLC: ocn754518563",
     "author": [
       {
         "family": "Suber",
@@ -392,7 +392,7 @@
         [
           "2019",
           5,
-          14
+          17
         ]
       ]
     }

variables.json

@@ -1,5 +1,5 @@
 {
-  "date": "May 14, 2019",
+  "date": "May 17, 2019",
   "authors": [
     {
       "github": "johndoe",
@@ -46,7 +46,7 @@
     "repo_slug": "manubot/rootstock",
     "repo_owner": "manubot",
     "repo_name": "rootstock",
-    "commit": "5da1d32778f1ed1aa6fdc64b9614acadc7103bf3"
+    "commit": "dcb3cc43880694acf4ea25774fabe328f20c3adb"
   },
   "manuscript_stats": {
     "reference_counts": {