Switch GIT_REPO from gitbox to github

github is encouraged for availability and high usage

 patch by Mick Semb Wever; reviewed by Brandon Williams

ccmlib/repository.py

@@ -31,8 +31,8 @@
 DSE_ARCHIVE = "http://downloads.datastax.com/enterprise/dse-%s-bin.tar.gz"
 OPSC_ARCHIVE = "http://downloads.datastax.com/enterprise/opscenter-%s.tar.gz"
 ARCHIVE = "http://archive.apache.org/dist/cassandra"
-GIT_REPO = "https://gitbox.apache.org/repos/asf/cassandra.git"
-GITHUB_REPO = "https://github.com/apache/cassandra.git"
+GIT_REPO = "https://github.com/apache/cassandra.git"
+GITHUB_REPO = "https://github.com/apache/cassandra"
 GITHUB_TAGS = "https://api.github.com/repos/apache/cassandra/git/refs/tags"
 CCM_CONFIG = ConfigParser.RawConfigParser()
 CCM_CONFIG.read(os.path.join(os.path.expanduser("~"), ".ccm", "config"))