Build and install from GOPATH

* Rename 'vendor/src' -> 'vendor'
  * Ignore vendor/ instead of vendor/src/ for lint
* Rename 'cmd/client' -> 'cmd/ocic' to make it 'go install'able
* Rename 'cmd/server' -> 'cmd/ocid' to make it 'go install'able
* Update Makefile to build and install from GOPATH
* Update tests to locate ocid/ocic in GOPATH/bin
* Search for binaries in GOPATH/bin instead of PATH
* Install tools using `go get -u`, so they are updated on each run

Signed-off-by: Jonathan Yu <jawnsy@redhat.com>

vendor/github.com/containers/storage/pkg/homedir/homedir.go

@@ -0,0 +1,39 @@
+package homedir
+
+import (
+	"os"
+	"runtime"
+
+	"github.com/opencontainers/runc/libcontainer/user"
+)
+
+// Key returns the env var name for the user's home dir based on
+// the platform being run on
+func Key() string {
+	if runtime.GOOS == "windows" {
+		return "USERPROFILE"
+	}
+	return "HOME"
+}
+
+// Get returns the home directory of the current user with the help of
+// environment variables depending on the target operating system.
+// Returned path should be used with "path/filepath" to form new paths.
+func Get() string {
+	home := os.Getenv(Key())
+	if home == "" && runtime.GOOS != "windows" {
+		if u, err := user.CurrentUser(); err == nil {
+			return u.Home
+		}
+	}
+	return home
+}
+
+// GetShortcutString returns the string that is shortcut to user's home directory
+// in the native shell of the platform running on.
+func GetShortcutString() string {
+	if runtime.GOOS == "windows" {
+		return "%USERPROFILE%" // be careful while using in format functions
+	}
+	return "~"
+}