0.99.2 - Third release candidate

What's Changed

• Header writing to a separate function by @CelliesProjects in #8
• Download tiles in a separate function by @CelliesProjects in #9
• Fix invalid tile messages by @CelliesProjects in #10
• Change function name setResolution to setSize by @CelliesProjects in #11
• Delete saveImage code by @CelliesProjects in #12
• Add RAII wrapper to HTTPClient by @CelliesProjects in #13
• Fix codacy warning about deleted ctors by @CelliesProjects in #14
• Add a RAII wrapper around pngdec by @CelliesProjects in #15

Full Changelog: 0.99.1...0.99.2