Make npm package a bit smaller

[macbre]

npm notice package size: 22.1 kB
npm notice unpacked size: 120.2 kB
npm notice total files: 35

vs

npm notice package size: 66.2 kB
npm notice unpacked size: 433.5 kB
npm notice total files: 73

[macbre]

Without files blacklist

$ npm publish --dry-run 2>&1 | egrep 'size|files'
npm notice package size:  46.9 kB                                 
npm notice unpacked size: 202.5 kB                                
npm notice total files:   71                          

With files blacklist

$ npm publish --dry-run 2>&1 | egrep 'size|files'
npm notice package size:  21.7 kB                                 
npm notice unpacked size: 119.0 kB                             
npm notice total files:   33