Explicitly use 'exit 1' to exit

Fixes #286

Using `exit $?` will exit with 0 status even in error conditions. I
believe this is due to the fact that the `if` statement sets `$?`
somehow. This could be a bug in the version of `bash` I'm using (as
`/bin/sh`):

```
$ /bin/sh --version
GNU bash, version 4.3.30(1)-release (x86_64-unknown-linux-gnu)
```
No need to output -1 since error codes are straightened out.
Merge pull request #287 from lukebakken/issues/lrb/286

Explicitly use 'exit 1' to exit