Remove first argument to `by`

I've tried to make all the changes to remove the first argument to `by` from discussion in #517 

Lots of small changes in many files, so, it's likely that I forgot something.
Looks like a typo here.  You should be able to run tests locally with 

```
pip install pytest
py.test --doctest-modules --verbose --pyargs blaze
```

Personally I do the following

```
pip install pytest conttest
cd /path/to/blaze
conttest "clear && py.test --doctest-modules --verbose --pyargs blaze"
```

This runs tests every time I save a file in that directory