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.
git bisect identified 62dd1d4 as the breaking commit; when
github.com/spf13/viper was introduced, the Params field was always
empty.
Given a map in YAML in Viper, the return type is
`map[interface{}]interface{}`, _not_ `map[string]interface{}`, even if
`.SetDefault()` has been called with an item of
`map[string]interface{}{}` so the cast assertion on the `.Get("Params")`
always failed.
Viper stores Permalinks as a map[string]interface{}, so the type assertion
to PermalinkOverrides (map[string]PathPattern) will always fail.
We can, however, get Permalinks as a map[string]string, and convert each
value to a PathPattern.
Be able to inhibit AbsURL canonicalization of content, on a site
configuration basis. Advantages of being able to inhibit this include
making it easier to rendering on other hostnames, and being able to
include resources on http or https depending on how this page was
retrieved, avoiding mixed-mode client complaints without adding latency
for plain http.
A sample config.yaml for a site might contain:
```yaml
permalinks:
post: /:year/:month/:title/
```
Then, any article in the `post` section, will have the canonical URL
formed via the permalink specification given.
Signed-off-by: Noah Campbell <noahcampbell@gmail.com>