Fixes #227

Checklist

• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the [Contribution Guide] and my PR follows them.
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added in line documentation to the code I modified

Short description of what this PR does:

• Added the gometalinter to the TravisCI build
• Enabled the following linters errcheck,vet,vetshadow,megacheck for starters.
• Invoked gometalinter twice in the following paths: . and helpers/... to avoid numerous warnings in the examples folder.
• Fixed a few small issues found by the enabled linters.

gometalinter --disable-all --enable=errcheck --enable=vet --enable=vetshadow --enable=megacheck helpers/...
helpers/inbound/inbound.go:70::warning: declaration of "err" shadows declaration at helpers/inbound/inbound.go:67 (vetshadow)
helpers/inbound/inbound.go:165::warning: declaration of "value" shadows declaration at helpers/inbound/inbound.go:149 (vetshadow)
helpers/inbound/inbound.go:169::warning: declaration of "header" shadows declaration at helpers/inbound/inbound.go:153 (vetshadow)
helpers/inbound/inbound.go:211:22:warning: error return value not checked (http.ListenAndServe(port, nil)) (errcheck)

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