Prep for v1.1.0

[odow]

A big diff: v1.0.3...master

Highlights:

• Clang used to fully wrap the C API
• Support for ScalarNonlinearFunction in the MOI wrapper
• Many many more tests, so that we now have 100% (excluding 1 @static line) code coverage
• All backwards compatible with no breaking changes

Since I've been making quite a few changes, I'll hold off on merging this until I get a few people to check it over.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.87%. Comparing base (ca79234) to head (9148b8c).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #242   +/-   ##
=======================================
  Coverage   99.87%   99.87%           
=======================================
  Files           2        2           
  Lines         777      777           
=======================================
  Hits          776      776           
  Misses          1        1           

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[odow]

Move this to JuMP-dev, update any URLs, and then tag.