Use MK v0.10.x, zap legacy GeoIP, build also on Linux (#29)

* Gopkg.lock: use MK v0.10.3

* ooni: stop using legacy GeoIP database files

* Some yak shaving of Makefile

1. remove now broken commands to download deps

2. also define the CXX cross compiler

* chore(dep): migrate from dep to go 1.11+ modules

See https://blog.callr.tech/migrating-from-dep-to-go-1.11-modules/

I need this to simplify my life in building for Travis.

* Introduce build.sh and repair build

In going forward, I believe we don't actually need a Makefile but I
didn't want to make such a radical change now.

* Another strategy wrt gopath

* travis: run regress tests on macOS

Closes #30

Makefile

@@ -1,29 +1,28 @@
 GO ?= go
 
 install-dev-deps:
-	@$(GO) get -u github.com/golang/dep/...
 	@$(GO) get golang.org/x/tools/cmd/cover
 	@$(GO) get github.com/mattn/goveralls
 
 build:
 	@echo "Building dist/ooni"
-	@$(GO) build -i -o dist/ooni cmd/ooni/main.go
+	@$(GO) build -o dist/ooni cmd/ooni/main.go
 .PHONY: build
 
 build-windows:
-	@echo "Building dist/ooni.exe"
-	CC=x86_64-w64-mingw32-gcc GOOS=windows GOARCH=amd64 CGO_ENABLED=1 go build -o dist/ooni.exe -x cmd/ooni/main.go
+	@echo "Building dist/windows/amd64/ooni.exe"
+	@./build.sh windows
 
-build-all: build build-windows
-.PHONY: build-all
+build-linux:
+	@echo "Building dist/linux/amd64/ooni"
+	@./build.sh linux
 
-download-mk-libs:
-	@echo "updating mk-libs"
-	@cd vendor/github.com/measurement-kit/go-measurement-kit && ./download-libs.sh
-download-mk-libs-macos:
-	@echo "updating mk-libs"
-	@cd vendor/github.com/measurement-kit/go-measurement-kit && ./download-libs.sh macos
-.PHONY: update-mk-libs-macos
+build-macos:
+	@echo "Building dist/macos/amd64/ooni"
+	@./build.sh macos
+
+build-all: build-windows build-linux build-macos
+.PHONY: build-all build-windows build-linux build-macos
 
 bindata:
 	@$(GO) run vendor/github.com/shuLhan/go-bindata/go-bindata/*.go \