move creating the stacktrace.log file higher

Summary: I'm seeing lots of crashes which don't have this file. I would like to make it as early as possible. I tested, and this syscall makes a file with:

```
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

int main() {
  open("/tmp/a.log", O_CREAT|O_TRUNC|O_WRONLY, S_IRUSR|S_IWUSR);
  raise (SIGKILL);
}
```

Reviewed By: @markw65

Differential Revision: D1535010
move creating the stacktrace.log file higher

Summary: I'm seeing lots of crashes which don't have this file. I would like to make it as early as possible. I tested, and this syscall makes a file with:

```
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

int main() {
  open("/tmp/a.log", O_CREAT|O_TRUNC|O_WRONLY, S_IRUSR|S_IWUSR);
  raise (SIGKILL);
}
```

Reviewed By: @markw65

Differential Revision: D1535010
Allow specifying a path to siege, add version check

Summary: Siege 3.0.0-3.0.7 are broken on ports other than :80 and :443.
rrh contacted the author, and a fix is expected in 3.0.8. Allow specifying the path.

refs facebook/hhvm#3664

Reviewed By: @ptarjan

Differential Revision: D1543417