This commit fixes#279 where a case of duplicate table headers slipped
through the cracks. This also adds an option to disable this new
validation to allow Cargo to preserve backwards compatibility.
This commit completely rewrites this crate from the ground up,
supporting serde at the lowest levels as I believe serde support was
intended to do. This is a major change from the previous versions of
this crate, with a summary of changes being:
* Serialization directly to TOML is now supported without going through
a `Value` first.
* Deserialization directly from TOML is now supported without going
through a `Value`. Note that due to the TOML format some values still
are buffered in intermediate memory, but overall this should be at a
minimum now.
* The API of `Value` was overhauled to match the API of
`serde_json::Value`. The changes here were to:
* Add `is_*` accessors
* Add `get` and `get_mut` for one-field lookups.
* Implement panicking lookups through `Index`
The old `index` methods are now gone in favor of `get` and `Index`
implementations.
* A `Datetime` type has been added to represent a TOML datetime in a
first-class fashion. Currently this type provides no accessors other
than a `Display` implementation, but the idea is that this will grow
support over time for decomposing the date.
* Support for the `rustc-serialize` crate has been dropped, that'll stay
on the 0.2 and 0.1 release trains.
* This crate no longer supports the detection of unused fields, for that though
you can use the `serde_ignored` crate on crates.io
