Fix typo in the last chapter
de-conflict linking

on github the link was getting made into html like this:

"""
<a href="http://eukaryota.dathub.org" target="_blank"></a><a href="http://eukaryota.dathub.org">http://eukaryota.dathub.org</a>
"""

which is clearly wrong; over-eager markdown conversion (maybe specific to github-flavored).

Also, on the get-dat adventure, the link just doesn't work at all; you can't click it. I'm not sure why that is though.
Update 04-working-with-blobs.md

Fix typos and simplify wording
Merge pull request #18 from olizilla/patch-2

Update 04-working-with-blobs.md
Merge pull request #15 from eush77/typo

Fix typo in the last chapter
Merge pull request #16 from ajschumacher/patch-1

de-conflict linking
gh-pages update