Add id to glossary entry

This is needed to enable users jump to glossary entries.

tools/id4glossary.py

+#!/usr/bin/env python
+"""Pandoc filter to convert add ids to glossary entries.
+
+Usage:
+
+    pandoc source.md --filter=id4glossary.py --output=output.html
+"""
+import pandocfilters as pf
+
+def normalize_keyword(keyword):
+    """Normalize keyword for became id
+
+    - Replace white space with '-'
+    - Convert to lowercase"""
+    return keyword.lower().replace(' ', '-')
+
+def keyword2html(keyword_node):
+    """Return HTML version of keyword with id."""
+    keyword = ' '.join([word['c'] for word in keyword_node if word['t'] == 'Str'])
+    id = normalize_keyword(keyword)
+    return [{"t": "Span",
+             "c": [[id, [],[]],
+                 keyword_node]}]
+
+def id4glossary(key, value, format, meta):
+    """Add id to keywords at glossary."""
+    if "subtitle" in meta and \
+            ''.join([string['c'] for string in meta["subtitle"]['c']]) == 'Reference':
+        if key == "DefinitionList":
+            for definition in value:
+                definition[0] = keyword2html(definition[0])
+            return {"t": key,
+                    "c": value}
+
+if __name__ == '__main__':
+    pf.toJSONFilter(id4glossary)