remove unnecessary .npmignore

Because package.json has `files` field.

https://www.npmjs.org/doc/files/package.json.html#files
use istanbul-coveralls to simplify the script

https://github.com/shinnn/istanbul-coveralls
update dependencies, devDependencies and files
Merge pull request #26 from shinnn/patch

Bump deps / Remove .npmignore / Use istanbul-coveralls