[commands/new.go] Update theme.toml etc.

[commands/new.go] Update theme.toml etc.

- Add copyright years and author to the top of the file

- Write the current year from time.Now() to LICENSE.md

- Correct comment regarding `os.MkdirAll(p, 0777)`

- In createConfig(), split the `map[string]string` definition into
  multiple lines to facilitate future expansion.  Also add a trailing
  slash to sample "baseurl" definition.

- Update theme.toml template to match that listed at
  https://github.com/spf13/hugoThemes/blob/master/README.md#themetoml

  See #883 for an equivalent `struct` implementation