Parse animation

Update flate2 to the latest version

Parse imagelayer

Also add test for parsed image layers.
The test can be also used as an example off how one can get data from
the parsed map.

Parse rotation on entities

Add ColorValue to PropertyValue

Tilesets can have objects inside of them since Tiled 1.0,

this just adds a field to the Tile so that data may be parsed and accessed

README: update example, crate badge

Load in properties from the tiles

Load Tilesets From External Files

Fix Map::get_tileset_by_gid

Add keywords metadata to Cargo.toml

Add properties to Objects and parse properties as enums

Still need to parse properties.

Because I forgot. Again. :(

The attribute is called "type" but we were previously looking for
"obj_type".