Add inline table syntax.

Concrete proposal for the inline table syntax I first proposed in Issue #219. Here's a quick taste:

```
# They should look familiar and obvious
name = { first = "Tom", last = "Preston-Werner" }
point = { x = 1, y = 2 }

# They make tuples unnecessary by allowing mixed types (they are just tables, after all).
# Unlike tuples, they are self-documenting via the key names.
address = { proto = "http", ip = "10.0.0.1", port = 8080 }

# Arrays of tables with less hassle
points = [ { x = 1, y = 2, z = 3 },
           { x = 7, y = 8, z = 9 },
           { x = 2, y = 4, z = 8 } ]
```

This is about as brief as I could think to make it, so if there are specific issues that need clarifying, please bring them up.