1.1.0 - Multiple tile formats and providers support

What's Changed

• Add code to use multiple tile formats and providers by @CelliesProjects in #96
• Build a vector of ptrs to use in composeMap() by @CelliesProjects in #101
• Zero-fill tile buffer on fetch failure to avoid ghosting by @CelliesProjects in #102
• Thread-safe PNG decode: use thread_local instance/buffer by @CelliesProjects in #103

Full Changelog: 1.0.6...1.1.0