Update build-osx.md

Formatting tweak
Update build-osx.md

Link to boost, some clarification in the steps.
Increase Default Block Max Size
Merge pull request #267 from rog1121/Fix-Block-Size

Increase Default Block Max Size
Aim for current block, not depth + 1
Update version.h
Merge pull request #269 from rog1121/1.4-Invalids-Ban

Ban Old Forked 1.4 Peers now that 1.4 Branch has a new version