ensure that By.apply is a reduction
expr: by schema
expr: reduction schema maintains record shape
rename sql reductions to original column name
Use label rather than alias to rename reductions

as per
http://stackoverflow.com/questions/9187530/using-alias-for-select-as-in-sqlalchemy
data: sql: include grouping columns
streaming reductions for Python layer

This is a kludge that works only in a very limited setting.
We should implement scalar expressions and then use those.
py3 fix
add comment explaining large condition
fix imports in compute python
rename seq/Sequence, l/seq
Use miniconda for conda rather than pip

Recommended by asmeurer

See http://conda.pydata.org/docs/travis.html
Merge pull request #273 from mrocklin/working

Various fixes, often in SQL