note use of python 2.7+ only

Author: doersf

README.md

@@ -3,20 +3,16 @@
 This Python package is the official reference client for the Block.io payments API. To use this, you will need the Dogecoin, Bitcoin, or Litecoin API key(s) from <a href="https://block.io" target="_blank">Block.io</a>. Go ahead, sign up :)
 
 #### ATTENTION: Package name has changed from block_io to block-io for PyPi.
-#### COMPATIBILITY: Please use Python2.6+. Also compatible with Python 3.0+.
+#### COMPATIBILITY: Please use Python2.7+. Also compatible with Python 3.0+.
 
 ## Installation
 
 [Using virtualenv is recommended when installing Python packages](https://packaging.python.org/en/latest/installing.html#virtual-environments).
 
-Install the package using `pip` for **Python 3**:
+Install the package using `pip` for **Python 2.7+**:
 
     pip install block-io
 
-Install the package using `pip` for **Python 2** - backported hashlib is required:
-
-    pip install block-io hashlib==20081119
-
 ## Usage
 
 It's super easy to get started. In your Python shell, do: