docs(README): move to .rst extension

MANIFEST.in

@@ -7,4 +7,5 @@ recursive-include cubicweb_squareui/wdoc *
 recursive-include test/data bootstrap_cubes *.py
 include *.ini
 recursive-include debian changelog compat control copyright rules
-include cubicweb-squareui.spec
\ No newline at end of file
+include cubicweb-squareui.spec
+include README.rst

setup.py

@@ -47,7 +47,7 @@ author = __pkginfo__['author']
 author_email = __pkginfo__['author_email']
 classifiers = __pkginfo__['classifiers']
 
-with open(join(here, 'README')) as f:
+with open(join(here, 'README.rst')) as f:
     long_description = f.read()
 
 # get optional metadatas