Update Readme.md

Some documentation fixes.

While I generally like the README, I think it is still somewhat hard to get all the details, especially around aloc, in one reading go. You provide quite a few examples and they definitively help, but I would suggest, that you interleave them with the textual description. Right now, first the indexer options are listed and than all the examples are shown. If you could provide an explicit example right below the description (into the bullet list) at least I would have an easier time understanding the differences.

One example for the multi-dimensional-indexing section would also help. And maybe even another example for the itype section to visualize what problems might arise from indexes with different types.