replace belssings with blessed to be compatible on windows

Author: nighi

colour_runner/result.py

@@ -1,7 +1,7 @@
 from unittest import result
 from unittest.util import strclass
 
-from blessings import Terminal
+from blessed import Terminal
 from pygments import formatters, highlight
 try:
     # Python 2

setup.py

@@ -23,5 +23,5 @@
     ],
     keywords='unittest colour color output',
     packages=find_packages(),
-    install_requires=['blessings', 'pygments'],
+    install_requires=['blessed', 'pygments'],
 )