Add error handling to readme

Author: ddeboer

README.md

@@ -81,6 +81,39 @@ use Ddeboer\Transcoder\Transcoder;
 $transcoder->transcode('España', null, 'UTF-8'); 
 ```
 
+### Error handling
+
+PHP’s `mv_convert_encoding` and `iconv` are inconvenient to use because they 
+generate notices and warnings instead of proper exceptions. This library fixes
+that:
+
+
+```php
+use Ddeboer\Transcoder\Exception\UndetectableEncodingException;
+use Ddeboer\Transcoder\Exception\UnsupportedEncodingException;
+use Ddeboer\Transcoder\Exception\IllegalCharacterException;
+
+$input = 'España';
+ 
+try {
+    $transcoder->transcode($input);
+} catch (UndetectableEncodingException $e) {
+    // Failed to automatically detect $input’s encoding 
+}
+
+try {
+    $transcoder->transcode($input, null, 'not-a-real-encoding');
+} catch (UnsupportedEncodingException $e) {
+    // ‘not-a-real-encoding’ is an unsupported encoding 
+}
+
+try {
+    $transcoder->transcode('Illegal quotes: ‘ ’', null, 'iso-8859-1');
+} catch (IllegalCharacterException $e) {
+    // Curly quotes ‘ ’ are illegal in ISO-8859-1
+}
+```
+
 ### Transcoder fallback
 
 In general, `mb_convert_encoding` is faster than `iconv`. However, as `iconv`

tests/MbTranscoderTest.php

@@ -46,7 +46,11 @@ public function testDetectEncoding()
      */
     public function testUndetectableEncoding()
     {
-        $result = $this->transcoder->transcode('‘España’', null, 'windows-1252');
+        $result = $this->transcoder->transcode(
+            '‘curly quotes make this incompatible with 1252’',
+            null,
+            'windows-1252'
+        );
         $this->transcoder->transcode($result);
     }
 
@@ -63,7 +67,7 @@ public function getStrings()
     {
         return [
             ['‘España’', 'windows-1252'],
-            ['España', 'iso-8859-1']
+            ['‘España', 'iso-8859-1']
         ];
     }
 }