fixed error when doing -reporter SOME_REPORTER:somefile.txt

If you specified a file but no path (i.e. 'somefile.txt' rather than
'path/to/somefile.txt'), it would show an error...

ERROR: Failed to create folder at ''.

Tested with...

```
./xctool.sh -project xctool/xctool-tests/TestData/TestProject-Library/TestProject-Library.xcodeproj -scheme TestProject-Library test -reporter json-stream:/tmp/b/c/d.txt
```

and

```
./xctool.sh -project xctool/xctool-tests/TestData/TestProject-Library/TestProject-Library.xcodeproj -scheme TestProject-Library test -reporter json-stream:somefile.txt
```
bumping to v0.1.2