bumped version to v0.5.7

setup.py

@@ -4,7 +4,7 @@ from setuptools import setup
 
 setup(
     name='PySSTV',
-    version='0.5.6',
+    version='0.5.7',
     description='Python classes for generating Slow-scan Television transmissions',
     author=u'András Veres-Szentkirályi',
     author_email='vsza@vsza.hu',