Rollback word consistencty over entire codebase (ref. #139).

framework/db/Connection.php

@@ -66,7 +66,7 @@ use yii\caching\Cache;
  *     // ... executing other SQL statements ...
  *     $transaction->commit();
  * } catch(Exception $e) {
- *     $transaction->rollBack();
+ *     $transaction->rollback();
  * }
  * ~~~
  *

framework/db/Migration.php

@@ -64,14 +64,14 @@ class Migration extends \yii\base\Component
 		$transaction = $this->db->beginTransaction();
 		try {
 			if ($this->safeUp() === false) {
-				$transaction->rollBack();
+				$transaction->rollback();
 				return false;
 			}
 			$transaction->commit();
 		} catch (\Exception $e) {
 			echo "Exception: " . $e->getMessage() . ' (' . $e->getFile() . ':' . $e->getLine() . ")\n";
 			echo $e->getTraceAsString() . "\n";
-			$transaction->rollBack();
+			$transaction->rollback();
 			return false;
 		}
 		return null;
@@ -89,14 +89,14 @@ class Migration extends \yii\base\Component
 		$transaction = $this->db->beginTransaction();
 		try {
 			if ($this->safeDown() === false) {
-				$transaction->rollBack();
+				$transaction->rollback();
 				return false;
 			}
 			$transaction->commit();
 		} catch (\Exception $e) {
 			echo "Exception: " . $e->getMessage() . ' (' . $e->getFile() . ':' . $e->getLine() . ")\n";
 			echo $e->getTraceAsString() . "\n";
-			$transaction->rollBack();
+			$transaction->rollback();
 			return false;
 		}
 		return null;

framework/db/Transaction.php

@@ -25,7 +25,7 @@ use yii\base\InvalidConfigException;
  *     //.... other SQL executions
  *     $transaction->commit();
  * } catch(Exception $e) {
- *     $transaction->rollBack();
+ *     $transaction->rollback();
  * }
  * ~~~
  *
@@ -42,14 +42,14 @@ class Transaction extends \yii\base\Object
 	public $db;
 	/**
 	 * @var boolean whether this transaction is active. Only an active transaction
-	 * can [[commit()]] or [[rollBack()]]. This property is set true when the transaction is started.
+	 * can [[commit()]] or [[rollback()]]. This property is set true when the transaction is started.
 	 */
 	private $_active = false;
 
 	/**
 	 * Returns a value indicating whether this transaction is active.
 	 * @return boolean whether this transaction is active. Only an active transaction
-	 * can [[commit()]] or [[rollBack()]].
+	 * can [[commit()]] or [[rollback()]].
 	 */
 	public function getIsActive()
 	{