* Update gometalinter config
gometalinter now uses `maligned` instead of `aligncheck`
(https://github.com/alecthomas/gometalinter/pull/367), so we need to update our
config accordingly.
* Update gometalinter
* Disable gotype linter
gotype does not seem to play nicely with the gb vendor directory. In
particular, it wants each of our dependencies to be built and installed (see
https://github.com/golang/go/issues/10969), but (empirically) it will not
accept them being installed in `pkg` but insists on them being in `vendor/pkg`.
This presents a problem because `gb build` builds the packages into `pkg`
(which doesn't seem entirely unreasonable since `.` comes before `vendor` in
`$GOPATH`). `go install github.com/x/y` does install in `vendor/pkg` but
requires us to know the name of each package.
The general conclusion of https://github.com/alecthomas/gometalinter/issues/91
seems to have been that the easiest thing to do is to disable `gotype` for now.
* Fix `unparam` lint
* Fix goshadow lint
