improve readme

Author: lajosbencz

README.md

@@ -1,2 +1,26 @@
 # php-stream-parse-sql
 PHP library to parse large SQL files command-by-command
+
+It's not a real SQL parser though, it only cares about command integrity, but not syntax.
+
+### Install:
+
+```
+composer require lajosbencz/stream-parse-sql
+```
+
+### Usage:
+
+```php
+$parser = new LajosBencz\StreamParseSql\StreamParseSql("./my/large/file.sql");
+$parser->onProgress(function($position, $size) {
+    echo ($position / $size) * 100, PHP_EOL;
+});
+foreacH($parser->parse() as $sqlCommand) {
+    /** @var stdClass $myDb some database adapter */
+    $myDb->execute($sqlCommand);
+}
+```
+
+### Todo:
+ * Extensively test if any input can produce a malformed command