Fix build not working on Windows

With this patch, building is actually possible.

However, for some reason onejs does not bundle the 'english-time' package into 7min.js, so I can't do anything useful with it. Here's the output I get when adding -d:

```
  one:package New package: 7min (index.js) +0ms
  one:requires index requires: ./lib/timer, ./lib/view +0ms
  one:requires lib\timer requires: new-format, ./templates, ./countdown, ./exercises, ./progress +1ms
  one:requires lib\countdown requires: iter, after-time, new-format, ./current, ./play, ./templates +2ms
  one:requires lib\current requires: attr +2ms
  one:package New package: attr (D:Source\JS\7min.io\node_modules\attr\index.js) +14ms
  one:requires io\node_modules\attr\index requires: new-pubsub, new-prop +3ms
  one:requires lib\play requires: ./current, ./exercises +3ms
  one:requires lib\exercises requires: ./program, ./exercise, ./current +2ms
  one:requires lib\exercise requires: new-format, ./current, ./templates +1ms
  one:package New package: new-format (D:Source\JS\7min.io\node_modules\new-format\index.js) +9ms
  one:package New package: iter (D:Source\JS\7min.io\node_modules\iter\index.js) +13ms
  one:package New package: after-time (D:Source\JS\7min.io\node_modules\after-time\index.js) +1ms
  one:requires io\node_modules\after-time\index requires: english-time +17ms
  one:requires lib\progress requires: new-format, ./exercises, ./current, ./templates +12ms
  one:requires lib\view requires: dom, event, ./current, ./timer, ./countdown, ./exercises, ./progress +27ms
  one:package New package: dom (D:Source\JS\7min.io\components\component-dom\index.js) +75ms
  one:requires io\components\component-dom\index requires: delegate, classes, indexof, domify, event, value, query, type, css +36ms
  one:package New package: delegate (D:Source\JS\7min.io\components\component-delegate\index.js) +13ms
  one:requires io\components\component-delegate\index requires: matches-selector, event +13ms
  one:package New package: matches-selector (D:Source\JS\7min.io\components\component-matches-selector\index.js) +4ms
  one:requires io\components\component-matches-selector\index requires: query +5ms
  one:package New package: query (D:Source\JS\7min.io\components\component-query\index.js) +3ms
  one:package New package: event (D:Source\JS\7min.io\components\component-event\index.js) +2ms
  one:package New package: classes (D:Source\JS\7min.io\components\component-classes\index.js) +1ms
  one:requires io\components\component-classes\index requires: indexof +4ms
  one:package New package: indexof (D:Source\JS\7min.io\components\component-indexof\index.js) +2ms
  one:package New package: domify (D:Source\JS\7min.io\components\component-domify\index.js) +2ms
  one:package New package: value (D:Source\JS\7min.io\components\component-value\index.js) +1ms
  one:requires io\components\component-value\index requires: type +6ms
  one:package New package: type (D:Source\JS\7min.io\components\component-type\index.js) +3ms
  one:package New package: css (D:Source\JS\7min.io\components\component-css\index.js) +2ms
  one:api Initialized at package.json +0ms
  one:options SourceURLs & verbose mode enabled +0ms
  one:api Output written into dist/7min.js. +54ms
```

The english-time package is correctly installed by npm and located in 7min.io\node_modules\after-time\node_modules\english-time.