Composer: Force Parsedown 1.8.0-beta-7 and Parsedown Extra 0.8.0-beta-1

A few days ago Parsedown released new ("stable") versions of Parsedown and Parsedown Extra: Parsedown 1.7.4 and Parsedown Extra 0.8.1. Parsedown 1.7.4 backports some features of Parsedown 1.8.0-beta-7 and is compatible with Parsedown Extra 0.8.1. However, due to these changes Parsedown Extra 0.8.1 now breaks compatibility with Parsedown 1.8.0-beta-7. Parsedown's release process is messed up beyond repair... Not sure what we're going to do now, this needs some research whether we can downgrade to Parsedown 1.7.4 without breaking things (what would require us to release a new major release, i.e. Pico 3.0). For now we're pinning Parsedown 1.8.0-beta-7 and Parsedown Extra 0.8.0-beta-1 as of Pico 2.1.0.

composer.json

@@ -34,8 +34,8 @@
         "php": ">=5.3.6",
         "twig/twig": "^1.36",
         "symfony/yaml" : "^2.8",
-        "erusev/parsedown": "~1.8.0|1.8.0@beta",
-        "erusev/parsedown-extra": "~0.8.0|0.8.0@beta"
+        "erusev/parsedown": "1.8.0-beta-7",
+        "erusev/parsedown-extra": "0.8.0-beta-1"
     },
     "suggest": {
         "picocms/pico-theme": "Pico requires a theme to actually display the contents of your website. This is Pico's official default theme.",