Document Typescript import

Some people would expect CommonJS-style `import bel = require('bel')` to work, but alas, it doesn't, although the compiled code still works. The way the definition file is set up the only way to import the module without errors is via `import bel from 'bel'` which seems counter-intuitive.

Can we document `import bel from 'bel'`? _Or_ add an `export = ` line to make `import bel = require('bel')` work?