Bulk IPv6 address creation is broken

[jeremystretch]

Issue type: Bug report

Python version: 2.7.6
NetBox version: 1.9.1

As reported by Didrik on the mailing list, there is a bug affecting the bulk creation of IPv6 addresses. This can be observed by attempting to create a range of IPv6 addresses as such:

2001:db8::[100,200,300]/128

This is expected to create three IPv6 addresses, however it creates 669 addresses. This is due to a bug in the parse_numeric_range() utility function which does not correct cast the beginning of a range to the appropriate numeric base. Thus, instead of returning e.g. range(256, 257) it returns range(100, 257).