Test matrix

[caspiano]

Creates a test matrix with the range given in the shard.yml.

This was done to show an issue with type annotations introduced in the 1.2.0 release candidate.

It also looks like this has unearthed some issues against crystal versions in the >= 0.34.0, <= 0.35.1 range

[kostya]

can you update shard.yml to >= 0.36.1, and skip older versions from testing?, also i not think nightly test needed

[caspiano]

I set the nightly test because I caught a bug that would have shown up in 1.2.0 if I hadn't tested this library against nightly.
The matrix is configured such that if nightly fails, the suite will not be marked as failing.

See crystal-lang/crystal#11308

[caspiano]

I've updated the version range to just >= 0.36.1.
See here for reasoning.