Update download_url for release v1.7.4 in setup.py (#48)

Author: iMichka

setup.py

@@ -14,7 +14,7 @@
       maintainer_email="[email protected]",
       description="Python package for easy C++ declarations navigation.",
       url="https://github.com/gccxml/pygccxml",
-      download_url="https://github.com/gccxml/pygccxml/archive/master.zip",
+      download_url="https://github.com/gccxml/pygccxml/archive/v1.7.4.tar.gz",
       license="Boost",
       keywords="C++, declaration parser, CastXML, gccxml",
       packages=["pygccxml",