Fixed issue (line length) with kml.py that kept pep8 test from passing.

.travis.yml

@@ -17,7 +17,7 @@ install:
 
 # command to run tests, e.g. python setup.py test
 script:
-#    - pep8 --exclude test_main.py fastkml
+    - pep8 --exclude test_main.py fastkml
     - coverage run --source=fastkml setup.py test
 
 after_success:

fastkml/kml.py

@@ -577,7 +577,9 @@ class _Container(_Feature):
                 yield feature
             else:
                 raise TypeError(
-                    "Features must be instances of (Folder, Placemark, Document)")
+                    "Features must be instances of "
+                    "(Folder, Placemark, Document)"
+                )
 
     def etree_element(self):
         element = super(_Container, self).etree_element()
@@ -591,7 +593,8 @@ class _Container(_Feature):
             self._features.append(kmlobj)
         else:
             raise TypeError(
-                "Features must be instances of (Folder, Placemark, Document)"
+                "Features must be instances of "
+                "(Folder, Placemark, Document)"
             )
         assert(kmlobj != self)