Piston Renderer example

modified objects to take floats instead of integers

Fix doc comment

Update for warnings

This commit also fixes a bug that meant the last cell of each row would
not be parsed if the tmx file was base64 encoded.

Enable a feature and use split instead of splitn, whose meaning has
changed.

Fix for "private type in exported type signature"

|&:p| is no longer valid syntax. It is inferred.

Update to rust nightly

Additional file support (zlib/uncompressed, gzip)

Split up decoding and uncompression in differenent functions.
Added support for base64/uncompressed.

Updated the example in the README

The new io crate is used in flate so tiled has been updated to use it as
well.

Thew new io crate gets rid of methods like read_u32_le, so we have to do
it ourselves.