* Lossless image optimization (using ImageOptim).
This shouldn't change the visual appearance of any images. ImageOptim
was run with the highest compression setting except that JPEG metadata
stripping was disabled because some users prefer to avoid stripping
JPEG metadata.
* Update READMEs that have Changelogs for themes impacted by lossless image optmization change.
* Update header.html
Change the vertical alignment of the header so that both site title and nav sit on the baseline.
* Update readme.txt
Minor updates to the readme file.