Misc. source comment typos (#391)

Found via `codespell -q 3`

Author: luzpaz

html5lib/_inputstream.py

@@ -461,7 +461,7 @@ def determineEncoding(self, chardet=True):
         if charEncoding[0] is not None:
             return charEncoding
 
-        # If we've been overriden, we've been overriden
+        # If we've been overridden, we've been overridden
         charEncoding = lookupEncoding(self.override_encoding), "certain"
         if charEncoding[0] is not None:
             return charEncoding

html5lib/serializer.py

@@ -274,7 +274,7 @@ def serialize(self, treewalker, encoding=None):
                 if token["systemId"]:
                     if token["systemId"].find('"') >= 0:
                         if token["systemId"].find("'") >= 0:
-                            self.serializeError("System identifer contains both single and double quote characters")
+                            self.serializeError("System identifier contains both single and double quote characters")
                         quote_char = "'"
                     else:
                         quote_char = '"'

html5lib/tests/serializer-testdata/core.test

@@ -375,7 +375,7 @@
                     "-//W3C//DTD HTML 4.01//EN"
                 ]
             ],
-            "description": "HTML 4.01 DOCTYPE without system identifer"
+            "description": "HTML 4.01 DOCTYPE without system identifier"
         },
         {
             "expected": [
@@ -389,7 +389,7 @@
                     "http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd"
                 ]
             ],
-            "description": "IBM DOCTYPE without public identifer"
+            "description": "IBM DOCTYPE without public identifier"
         }
     ]
 }

setup.py

@@ -46,7 +46,7 @@ def default_environment():
 
     _markerlib.default_environment = default_environment
 
-# Avoid the very buggy pkg_resources.parser, which doesnt consistently
+# Avoid the very buggy pkg_resources.parser, which doesn't consistently
 # recognise the markers needed by this setup.py
 # Change this to setuptools 20.10.0 to support all markers.
 if pkg_resources: