Revert "Migrate as much as possible to pip and requirements.txt"

This reverts commit 982594a4a5.

lib/yaml/loader.py

@@ -0,0 +1,40 @@
+
+__all__ = ['BaseLoader', 'SafeLoader', 'Loader']
+
+from reader import *
+from scanner import *
+from parser import *
+from composer import *
+from constructor import *
+from resolver import *
+
+class BaseLoader(Reader, Scanner, Parser, Composer, BaseConstructor, BaseResolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        BaseConstructor.__init__(self)
+        BaseResolver.__init__(self)
+
+class SafeLoader(Reader, Scanner, Parser, Composer, SafeConstructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        SafeConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class Loader(Reader, Scanner, Parser, Composer, Constructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        Constructor.__init__(self)
+        Resolver.__init__(self)
+