Update the project version from 0.1.4 to 0.1.5 across the codebase,
specifically in mix.exs and the README.md installation instructions.
The dependency crucible_datasets is updated to version 0.5.4, which
results in an update for crucible_ir to 0.2.1 in the lockfile.

The CHANGELOG.md is updated to record these changes for the 0.1.5
release date of 2025-12-28.