allows multiple authors--use ';' in list, also corrects assets dir

Provides two patches for the current gem version (listed as 0.0.2):

1. Allows multiple authors to be listed correctly in epub, mobi. List authors in `.wordsmith` file as a ';' semi-colon-separated list. 
1. Corrects generate to find assets dir, rather than based on template.

I also made a tag for the 0.0.2 version that is listed as a gem. This will be handy if/until there's an update to 0.0.3