job leader process

Implement a separate process, the "leader", which runs all the
scripts for a job run, instead of directly from the main laminard
process. This makes for a cleaner process tree view, where the
owning job for a given script is clear; also the leader process
acts as a subreaper to clean up any wayward descendent processes.

Resolves #78.

test/main.cpp

@@ -18,10 +18,22 @@
 ///
 #include <kj/async-unix.h>
 #include <gtest/gtest.h>
+#include <kj/debug.h>
 
-// gtest main supplied in order to call captureChildExit
+#include "laminar-fixture.h"
+#include "leader.h"
+
+// gtest main supplied in order to call captureChildExit and handle process leader
 int main(int argc, char **argv) {
+    if(argv[0][0] == '{')
+        return leader_main();
+
+    // TODO: consider handling this differently
+    auto ioContext = kj::setupAsyncIo();
+    LaminarFixture::ioContext = &ioContext;
+
     kj::UnixEventPort::captureChildExit();
+    //kj::_::Debug::setLogLevel(kj::_::Debug::Severity::INFO);
 
     ::testing::InitGoogleTest(&argc, argv);
     return RUN_ALL_TESTS();