osbuild-composer: Rename module to github.com/osbuild/osbuild-composer

This should be the best practice according to other popular go projects:
- https://github.com/prometheus/prometheus
- https://github.com/syncthing/syncthing
- https://github.com/drone/drone
- https://github.com/hashicorp/terraform

Also, this change fixes go get command (it currently fails due to bad package
name).

internal/store/store.go

@@ -4,12 +4,12 @@ package store
 
 import (
 	"encoding/json"
+	"github.com/osbuild/osbuild-composer/internal/blueprint"
+	"github.com/osbuild/osbuild-composer/internal/pipeline"
+	"github.com/osbuild/osbuild-composer/internal/target"
 	"io/ioutil"
 	"log"
 	"os"
-	"osbuild-composer/internal/blueprint"
-	"osbuild-composer/internal/pipeline"
-	"osbuild-composer/internal/target"
 	"path/filepath"
 	"sort"
 	"sync"