Write to the same directory as the input file

This only happens if the output file is specified in the YAML prefix, no
output file was given on the commandline, the specified output file is
only a file name *and* the input file is not in the current directory.

It ensures that `blog /some/path/to/blog.yaml` doesn't generate a file
in the current directory if the output was specified as `output: file.yaml`.

go/blog/blog.go

	"io/ioutil"
	"net/url"
	"os"
	"path"
	"sort"
	"strings"
	"unicode"
		// write to specified `output` file if none was given as an argument
		if opts.Output != "" && out == os.Stdout {
			// write to same directory as the input file if opts.Output is
			// just the file name
			if path.Base(opts.Output) == opts.Output && path.Dir(dataPath) != "." {
				opts.Output = path.Join(path.Dir(dataPath), opts.Output)
			}
			out, err = os.Create(opts.Output)
			if err != nil {
				exit(err)