Update header.c

change to c89

Fix dependency instructions for macOS

Update to version 2.0.0

Minor fixes

Adds max scale option to prevent over-sizing

Adds export method

Switches to simpler interface for composite

Merge pull request davidbyttow#32 from davidbyttow/d/imagetype

Return final image type from Apply

Rearranges package layout to be more standard

Merge pull request davidbyttow#25 from Nafanya/feature/rotation

Add rotation operation