run CI on Julia 1.0 as well

[bicycle1885]

• Run CI on Julia 1.0 as well as 0.7.
• Modernize the AppVeyor script.
• Disallow failure on nightly because it should be backward-compatible.

[codecov]

Codecov Report

Merging #45 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #45   +/-   ##
=======================================
  Coverage   97.65%   97.65%           
=======================================
  Files           3        3           
  Lines         596      596           
=======================================
  Hits          582      582           
  Misses         14       14

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a45870b...2d409b6. Read the comment docs.