Small fixes to the new way we handle pandoc releases (#298)

* Updated logic to get pandoc releases - issue #295

* Updated appveyor script

* Updated how get get the versions from GitHub, including handling of latest

* Performance enhancement suggested by @davidbgk

* Updated the way we get the version number from the fractured url

* Hey let's not dublicate the runners

.github/workflows/ci.yaml

@@ -1,8 +1,10 @@
 name: Continuous Integration
 
 on:
-  - push
-  - pull_request
+  pull_request:
+    paths:
+      - '**.py'
+      - '**.yaml'
 
 jobs:
   test:

pypandoc/pandoc_download.py

@@ -49,9 +49,8 @@ def _get_pandoc_urls(version="latest"):
     # try to open the url
     try:
         response = urlopen(url)
-        content = response.read()
-        pattern = re.compile(r"pandoc\s*([\d.]+)")
-        version = re.search(pattern, content.decode("utf-8")).group(1)
+        version_url_frags = response.url.split("/")
+        version = version_url_frags[-1]
     except urllib.error.HTTPError as e:
         raise RuntimeError("Invalid pandoc version {}.".format(version))
         return