xrange alias not propogating so we need to set it explicitly in some places (#268)

voltron/plugins/__init__.py

@@ -0,0 +1,2 @@
+if not hasattr(__builtins__, "xrange"):
+    xrange = range

voltron/plugins/debugger/__init__.py

@@ -0,0 +1,2 @@
+if not hasattr(__builtins__, "xrange"):
+    xrange = range

voltron/plugins/debugger/dbg_lldb.py

@@ -10,6 +10,8 @@ from voltron.api import *
 from voltron.plugin import *
 from voltron.dbg import *
 
+from voltron.plugins.debugger import xrange
+
 try:
     import lldb
     HAVE_LLDB = True