Use "nodefaults" in CI conda env file

See merge request !79

Add check if a MeshElementGroup is affine

See merge request !76

Fix curve closedness check in make_curve_mesh

See merge request !78

Boundary tag bit safer

See merge request !77

* check all elements, not just the first one
* check all second derivatives (including cross ones)
* add tests for all of that

Fix some links and typos in the docs

See merge request !75

Add CI job to test examples on Github

Test examples during CI

See merge request !74

Add cartoon DG solver

See merge request !70

Fix some remaining issues with 1D meshes

See merge request inducer/meshmode!71