feat: Add support for AMD/UMD modules.

Uses the @wilsonpage super wrapper to provide support for AMD and UMD as well as provide access via a global `crosstab` variable if no module loader is used.

Wrapper can be found at https://gist.github.com/wilsonpage/8598603

fixes #3.
Merge pull request #5 from shane-tomlinson/issue-3-amd-umd-support

feat: Add support for AMD/UMD modules.