Set default encoding to UTF-8 (#315)

* Add a note about how to install optional charset converter dependencies

Fixes part of #252 and #237.

* Default ircOptions.encoding to utf-8 if node-irc can convert encodings

Also warn when started if the IRC library cannot convert between
encodings, in case users rely on this behavior.

* Improve config check and warning message around encodings

README.md

@@ -37,6 +37,10 @@ import config from './config.json';
 discordIRC(config);
 ```
 
+When installing the library, you may encounter an error relating to the installation of `iconv` or `node-icu-charset-detector`.
+These are optional dependencies which allow you to set the target encoding of messages sent to Discord, as detailed below in the README.
+Without these dependencies and the relevant setting, messages that aren't sent in UTF-8 may be corrupted when copied to Discord.
+
 ## Configuration
 First you need to create a Discord bot user, which you can do by following the instructions [here](https://github.com/reactiflux/discord-irc/wiki/Creating-a-discord-bot-&-getting-a-token).
 
@@ -94,6 +98,13 @@ The `ircOptions` object is passed directly to irc-upd ([available options](https
 
 To retrieve a discord channel ID, write `\#channel` on the relevant server – it should produce something of the form `<#1234567890>`, which you can then use in the `channelMapping` config.
 
+### Encodings
+
+If you encounter trouble with some characters being corrupted from some clients (particularly umlauted characters, such as `ä` or `ö`), try installing the optional dependencies `iconv` and `node-icu-charset-detector`.
+The bot will produce a warning when started if the IRC library is unable to convert between encodings.
+
+Further information can be found in [the installation section of irc-upd](https://github.com/Throne3d/node-irc#character-set-detection).
+
 ## Tests
 Run the tests with:
 ```bash

lib/bot.js

@@ -91,6 +91,16 @@ class Bot {
       ...this.ircOptions
     };
 
+    // default encoding to UTF-8 so messages to Discord aren't corrupted
+    if (!Object.prototype.hasOwnProperty.call(ircOptions, 'encoding')) {
+      if (irc.canConvertEncoding()) {
+        ircOptions.encoding = 'utf-8';
+      } else {
+        logger.warn('Cannot convert message encoding; you may encounter corrupted characters with non-English text.\n' +
+          'For information on how to fix this, please see: https://github.com/Throne3d/node-irc#character-set-detection');
+      }
+    }
+
     this.ircClient = new irc.Client(this.server, this.nickname, ircOptions);
     this.attachListeners();
   }