Now, users can set content type explicitly for their files in a number of ways, or rely on automatic file-extension content types. Proxied files default to automatic file-extension content types, but then fall back to the content type of the resource they proxy to. There is also a bug fixed around correctly setting content type inside send_file. Fixes#821.
There are a few things changing here. One is that we always dup metadata before using it - this prevents a class of nasty bugs where after the first resource list build, blocks had been deleted from metadata hashes, meaning they would no longer be applied. Now they will always stick around. Then, I made sure that whenever we render a file, we save the previous I18n.locale and restore it afterwards, in case people change locale from blocks. This should help in some weird cases where files are rendered recursively. Finally, I've added a :lang option that can be used from "page" or "proxy" to allow people to specify the language for one or more files without having to pass a block that sets I18n.locale directly, which should make that pattern much cleaner. This fixes#809 and may also fixmiddleman/middleman-blog#106.
"set :trailing_slash, false" will cause resource urls that match the
index_file to have the trailing slash stripped off the directory URL,
e.g. instead of "/dir/index.html" becoming "/dir/" it will be "/dir"