python: support By(t, t, t.reduction())

Previously we expected the grouper to be a projection.  Now we allow it to be
any rowfuncable
specify sqlalchemy float types
CSV/SQL._extend([]) works
server: __init__.py
update travis.ymal and conda yaml to include toolz and cytoolz as runtime dependencies of blaze
Merge pull request #360 from quasiben/feature/conda_deps_update

Update runtime dependencies of blaze
sql: choose given schema if mismatch exists
Merge pull request #359 from mrocklin/small-fixes-2

Small fixes
Merge pull request #356 from mrocklin/sql-types

specify sqlalchemy float types
Merge pull request #354 from mrocklin/by-of-tablesymbol

python: support By(t, t, t.reduction())
expr: scalar date/datetime coercion
expr: basic unsafe exprify implementation
server: Selection API
py2.6 compatibility, dict comprehension
fix typo in docstring
Cleaner SQL for projections using .with_only_columns
Test datetime serialization