Fix mixed up min/max order.

D'oh. Noticed while writing file saving routines.
Remove unsafe withUnsafePointer usage.

No reason for it here. Need to pay more attention to the Swift docs.
Make seven characters minimum for hex color with alpha.

Bug had to do with my shoddy port of the original to/fromHexString code
over to Swift. The first iteration didn't even take into account the
"#" prefix, so it wasn't counted here.

      123456789
      #rrggbbaa
             ^ In other words, > 7.
plist: Filter out non-plists from settings array.

Hadn't considered there might be unexpected types in there, so it
should filter those out.
Incorrect downcast syntax.

Or, at least, weird downcast syntax...
scheme: Use QPropertyList, not NSDictionary.

Neither affords any type safety here since they're effectively the
same thing, but the swift dictionary is what I'm trying to use.
scheme: Add rule loading.
scheme: Get color settings from settings sub-dict.

Forgot to do this in reading rules as well.
scheme: "gutter", not "gutterBackground"

As is often the case, background is implied, foreground is explicit in
the names for these keys.
scheme: toPropertyList -- write rules, base settings sub-dict.

Was appending the settings dict to the baseRules array without first
wrapping it in a ["settings":settings] dict.

Besides that, the rules weren't even being written, nor was the UUID.
rule: Read plists properly/fully.

1-  The settings dictionary wasn't being read, so colors never got
    assigned.

2-  Scopes (informally selectors because they follow CSS-like selector
    behavior) weren't read at all.
rule: fix all of toPropertyList.

Now writes out the correct format:

  {
    name = "name";
    scope = "scope1, scope2";
    settings = {
      fontStyle = "italic bold underlined whathaveyou";
      foreground = "#rrggbbaa";
      background = "#rrggbbaa";
    };
  }
syntax: Remove odd optional casts.

Not much point to plist[key]? as? T, since plist[key] returns a Value?
optional anyway, so there's no need to force it to be optional.
document: Remove dummy data.
document: Throw in correct read/write stubs.
document: implement readFromURL.

Currently no way I'm aware of to handle this failing. Far as I know,
Swift still doesn't handle the idea of objects returning nil from their
initializers, so we'll see where that goes.
document: implement writeToURL.

Basically just the same thing as Obj-C Schemer.