Add better check style and code formatting

[chombium]

Add better check style and code formatting based on ESLint and refactor the souce code to reflect the changes

[chombium]

Browsing the source code of aedes mentioned by @mcollina in #32 I noticed that he used StandardJS for the project.
StandardJS looks really nice and since it works out of the box and there are no configuration files to maintain and adjust. I think it would be better option

[mcollina]

That's my idea :)

[chombium]

I added StandardJS and reformatted the code to conform it's rules. I didn't add StandardJS as a development dependency because code formatting and check style is something that is a must for every project. So I prefer using globally installed standardJS instead of duplication in each project.

I will create one big pull request together with the changes for #28 and #30 when I'm finished.

[chombium]

The changes have been merged into the master