Added optimal travis ci settings

[amilajack]

• Faster builds
• More stable tests (force npm installation to be latest version)

[medikoo]

Great thanks, if indeed that's an improvement I'll be happy to take it. I posted my doubts in comments

[amilajack]

What improvement that makes?

cache delcaration tells travis to cache the node_modules directory. This makes builds much faster.

Also global install doesn't make sense in case of this package as it doesn't expose any binaries

npm I -g npm@latest is the only global installation. What this line does is it overrides the default global version of npm and installs the latest version. Npm has a history of having bugs that made builds fail so its safest to use the one with the highest patch semvar.

[medikoo]

@amilajack thanks for clarifiction, I mistakenly assumed it's about global install of this package, which of course wasn't

[amilajack]

Thanks