[fix] shows abnormal whitespace production on insert

Furthermore, this shows an unexpected behaviour with the index in
a LineProxyList. The .insert(2, ...) should insert just before "class B"
but instead inserts after it. This is because the \n after "class A" is
merged with that node's value but it shouldn't.

Author: Pierre Penninckx

tests/test_insert.py

@@ -0,0 +1,76 @@
+#!/usr/bin/python
+# -*- coding:Utf-8 -*-
+
+""" Tests the code insertion features """
+
+import pytest
+# pylint: disable=redefined-outer-name
+from redbaron import RedBaron
+
+
+@pytest.fixture
+def red():
+    return RedBaron("""\
+class A:
+    pass
+
+class B:
+    pass
+""")
+
+
+def test_insert_with_class_0(red):
+    red.insert(0, "a = 1")
+
+    print(red.dumps())
+    assert red.dumps() == """\
+a = 1
+class A:
+    pass
+
+class B:
+    pass
+"""
+
+
+def test_insert_with_class_1(red):
+    red.insert(1, "a = 1")
+
+    print(red.dumps())
+    assert red.dumps() == """\
+class A:
+    pass
+a = 1
+
+class B:
+    pass
+"""
+
+
+def test_insert_with_class_2(red):
+    red.insert(2, "a = 1")
+
+    print(red.dumps())
+    assert red.dumps() == """\
+class A:
+    pass
+
+a = 1
+class B:
+    pass
+"""
+
+
+def test_insert_with_class_3(red):
+    red.insert(3, "a = 1")
+
+    print(red.dumps())
+    assert red.dumps() == """\
+class A:
+    pass
+
+class B:
+    pass
+a = 1
+"""
+