README: Add swagger-js-codegen.queries and fix closing punctuation

`swagger-js-codegen` has been a multi-task since 6173c732 (First
commit, 2014-06-15), and [multi-tasks need named sub-properties to
iterate over][1].  I don't see much point to both having a multi-task
and an array for `apis`.  Perhaps we should have:
    
    'swagger-js-codegen': {
      batch: {
        options: {
          api: {
            swagger: 'swagger/_batch.json',
            moduleName: 'Batch'
          },
          dest: 'lib'
        },
      },
      queries: {
        options: {
          api: {
            swagger: 'swagger/_queries.json',
            moduleName: 'Queries'
          },
          dest: 'lib'
        },
      },
    }
    
which would allow both the complete:
    
    $ grunt swagger-js-codegen
    
and the per-API:
    
    $ grunt swagger-js-codegen:queries
    
[1]: http://gruntjs.com/api/grunt.task#grunt.task.registermultitask