Updated change log

Updated the change log: small typo in 0.4dev and added/moved release dates into version headers.

Obviously, it is a style issue whether the release date should go into the version headers... so no problem to close this PR. However, do note the small typo and the release dates for 0.4 and 0.3.2
Merge pull request #127 from mdxs/patch-1

Updated change log