Fixing the taxonomy example. Fixed #318.
More taxonomy examples in templates.
Adding a page listing the different methods available to Taxonomies.
Making the Pages Sorting methods available within a taxonomy term.
Making the term "Term" more consistent with Taxonomy usage.
Switch .Data to .Pages in the PageGroup functionality for increased consistency.
Adding .Reverse() to PagesGroup
Making direction optional (and setting defaults) for GroupBy Pages functionality.
Added more examples and cleaned up the GroupBy functionality documentation
Adding documentation about 'where' and cleaning up docs around first.
Fix CreatePages

This fixes #450.  There are two problems:

1.) We're creating a new goroutine for every page.
2.) We're calling s.Pages = append(s.Pages, page) inside each goroutine.

1 is a problem if in that if you have a ton of pages, that's a ton of goroutines.  It's not really useful to have more than a few goroutines at a time, and lots can actually make your code much slower, and, evidently, crash.

2 is a problem in that append is not thread safe. Sometimes it returns a new slice with a larger capacity, when the original slice isn't large enough.  This can cause problems if two goroutines do this at the same time.

The solution for 1 is to use a limited number of workers (I chose 2*GOMAXPROCS as a nice guess).
The solution for 2 is to serialize access to s.Pages, which I did by doing it in a single goroutine.
Adjusting the number of go routines to build the pages in to 4*GOMAXPROCS (from 2) for faster rendering.
quickstart.md: Put long options inside backticks

Also minor adjustment to blank lines.