Fix broken travis tests

[wtgee]

There is ongoing work in #711, #712 and #713 to update some of the travis install for astrometry-net, but in light of the fact that astrometry.net website will be down for an unknown amount of time, this PR simply switches the URL to the github release page, which will unblock #709 and #710.

Edit: Also fixes numpy version to fix IERS import.

[jamessynge]

Thanks for extracting the critical bits from my exploratory PRs.

[codecov]

Codecov Report

Merging #714 into develop will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #714      +/-   ##
===========================================
- Coverage    80.09%   80.03%   -0.06%     
===========================================
  Files           61       61              
  Lines         5078     5078              
  Branches       693      693              
===========================================
- Hits          4067     4064       -3     
- Misses         817      820       +3     
  Partials       194      194

Impacted Files	Coverage Δ
pocs/dome/astrohaven.py	71.05% <0%> (-2.64%)	⬇️

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