try to fix error when install by npm

```
$ npm install insightjs
npm http GET https://registry.npmjs.org/insightjs
npm http 304 https://registry.npmjs.org/insightjs

> insightjs@0.1.4 postinstall /home/s991533/node_modules/insightjs
> bower install

sh: bower：command not found
npm WARN This failure might be due to the use of legacy binary "node"
npm WARN For further explanations, please read
/usr/share/doc/nodejs/README.Debian
 
npm ERR! weird error 127
npm ERR! not ok code 0
```
Merge pull request #109 from PeterDaveHello/patch-1

try to fix error when install by npm