test: add Drone tests

Also includes installation and development documentation, and updates
  to the latest development version of mkdocs-simple-plugin.

  Resolves #3.

mkdocs.yml

@@ -1,12 +1,14 @@
 site_name: MkDocs semiliterate plugin
 nav:
 - Overview: README.md
+- Installation: drone_install.md
 - Usage: mkdocs_semiliterate/plugin.md
+- Developing: drone_develop.md
 plugins:
 - search
 - semiliterate:
     merge_docs_dir: false
-    ignore_folders: [dist, build]
+    ignore_folders: [build, dist, tests]
     include_extensions: [LICENSE]
     semiliterate:
       - pattern: '(\.md)$'
@@ -15,6 +17,16 @@ plugins:
       - pattern: '(\.py)$'
         start: '"""\smd'
         stop: '"""'
+      - pattern: '.drone.yml'
+        destination: 'drone_develop.md'
+        start: '### develop'
+        stop: '^\s*###'
+        replace: ['^# (.*\s*)$', '^\s*-(.*\s*)$']
+      - pattern: '.drone.yml'
+        destination: 'drone_install.md'
+        start: '### install'
+        stop: '^\s*###'
+        replace: ['^# (.*\s*)$', '^\s*-(.*\s*)$']
 markdown_extensions:
 - abbr
 - def_list