Replace boost/filesystem with kj/filesystem

Lose the boost dependency since recent versions of capnproto's kj
also provide a nice filesystem library. Take the opportunity to
refactor the Run object to become more than POD and to encapsulate
some of the functionality that was done in the Laminar class

Part of #49 refactor

test/tempdir.h

@@ -0,0 +1,45 @@
+///
+/// Copyright 2018 Oliver Giles
+///
+/// This file is part of Laminar
+///
+/// Laminar is free software: you can redistribute it and/or modify
+/// it under the terms of the GNU General Public License as published by
+/// the Free Software Foundation, either version 3 of the License, or
+/// (at your option) any later version.
+///
+/// Laminar is distributed in the hope that it will be useful,
+/// but WITHOUT ANY WARRANTY; without even the implied warranty of
+/// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+/// GNU General Public License for more details.
+///
+/// You should have received a copy of the GNU General Public License
+/// along with Laminar.  If not, see <http://www.gnu.org/licenses/>
+///
+#ifndef LAMINAR_TEMPDIR_H_
+#define LAMINAR_TEMPDIR_H_
+
+#include <kj/filesystem.h>
+#include <stdlib.h>
+
+class TempDir {
+public:
+    TempDir() :
+        path(mkdtemp()),
+        fs(kj::newDiskFilesystem()->getRoot().openSubdir(path, kj::WriteMode::CREATE|kj::WriteMode::MODIFY))
+    {
+    }
+    ~TempDir() noexcept {
+        kj::newDiskFilesystem()->getRoot().remove(path);
+    }
+    kj::Path path;
+    kj::Own<const kj::Directory> fs;
+private:
+    static kj::Path mkdtemp() {
+        char dir[] = "/tmp/laminar-test-XXXXXX";
+        ::mkdtemp(dir);
+        return kj::Path::parse(&dir[1]);
+    }
+};
+
+#endif // LAMINAR_TEMPDIR_H_