npm ignore dist and test folders

This decreases the generated `tar.gz` published by 1MB.

# Before

```
> ls -alh less-1.4.2.tgz 
-rw-r--r--  1 kevin  staff   1.1M Aug  6 19:47 less-1.4.2.tgz
```

# After

```
> ls -alh less-1.4.2.tgz 
-rw-r--r--  1 kevin  staff    79K Aug  6 19:49 less-1.4.2.tgz

```