Investigate why Recast must be installed in regenerator/node_modules/recast rather than regenerator/../recast/

[benjamn]

~/node_modules/regenerator% rm -rf node_modules/recast
~/node_modules/regenerator% npm test

> regenerator@0.4.1 test /Users/benjamn/node_modules/regenerator
> node test/run.js

process exited abnormally: { [SyntaxError: Line 455: Illegal yield expression while parsing /Users/benjamn/node_modules/regenerator/test/tests.es5.js]
  filename: '/Users/benjamn/node_modules/regenerator/test/tests.es5.js' }