formatting: use emoji 2.0 style

The `use_aliases` argument was deprecated in `emoji` 1.7 and removed
in 2.0. It was replaced with the option `language='alias'`.
Update README.md to reflect this requirement.

Fixes #118. See also:
https://github.com/carpedm20/emoji/blob/d8bbfe455c6fcd12b96ed1dce6e0978fe7a47431/emoji/core.py#L95-L98

README.md

@@ -14,6 +14,14 @@ cd sopel-github
 pip install .
 ```
 
+### Emoji support
+
+If you intend to make use of the emoji support, emoji >= 1.7.0 is required, but
+emoji >= 2.0 is recommended.
+```
+pip install emoji>=2.0
+```
+
 ## Out-of-the-box Functionality
 
 Detects when GitHub URLs are posted and takes over URL handling of them, pretty

sopel_modules/github/formatting.py

@@ -28,7 +28,7 @@
 except ImportError:
     emojize = lambda text: text
 else:
-    emojize = lambda text: emoji.emojize(text, use_aliases=True)
+    emojize = lambda text: emoji.emojize(text, language='alias')
 
 current_row = None
 current_payload = None