Formulae that depend on `node` sometimes contain files that use a
shebang like `#!/usr/bin/env node` and this can lead to issues when
the `node` in a user's environment isn't brewed `node`.
For example, some node modules are compiled when the formula is built
but if the user's `node` is a different major version than brew's
`node`, the differing `NODE_MODULE_VERSION` can produce an error when
certain parts of the application are used. The formula may build and
test fine and the issue may only become apparent when more of the
application is exercised.
This adds a `Language::Node::Shebang` module (borrowing from the
existing Perl and Python examples), which allows us to use
`rewrite_shebang detected_node_shebang, ...` in formulae to address
this type of issue.
