Fix audit issues

Merge pull request #21 from joaquimserafim/v3.1.1

fix dev-dependencies sec issues

Merge pull request #20 from joaquimserafim/v3.0.1

fix vulnerabilities with dev dependencies

support only last versions of NodeJS

versions:

• 8
• 10
• 11

and update some the devs dependencies e reports

v2.1.3: Merge pull request #13 from joaquimserafim/v2.1

• add support to set optional reserved headers with the encode method

v2.0.3

don't throw an error when decode a bad token or header

v2.0.2

minor fixes in the package.json file

v2.0.1

fix module name

v2.0.0: Merge pull request #8 from joaquimserafim/node_4

update and refactoring for NodeJS >= 4

v1.6.3: Merge pull request #7 from joaquimserafim/support_node_4

add support for node 4 on travis

v1.5.3

v.1.5.3