Added plans for the future to README

Author: sybrenstuvel

README.md

@@ -21,12 +21,24 @@ Download and install using:
 
     pip install rsa
 
-or:
-
-    easy_install rsa
-
 or download it from the [Python Package Index](https://pypi.python.org/pypi/rsa).
 
 The source code is maintained at [Github](https://github.com/sybrenstuvel/python-rsa/) and is
 licensed under the [Apache License, version 2.0](https://www.apache.org/licenses/LICENSE-2.0)
 
+
+Plans for the future
+--------------------
+
+Version 3.4 is the last version in the 3.x range. Version 4.0 will drop the following modules,
+as they are insecure:
+
+- `rsa._version133`
+- `rsa._version200`
+- `rsa.bigfile`
+- `rsa.varblock`
+
+Those modules are marked as deprecated in version 3.4.
+
+Furthermore, in 4.0 the I/O functions will be streamlined to always work with bytes on all
+supported versions of Python.