expr: add path-split function
expr: Split function to chunk expressions
expr: split distinct operations, fix split
summary string printing
expr: split on summaries
wip: split expr on by, expose error on summary
expr: ensure that summary.child is not a reduction
expr: summary child must be tableexpr
ensure that path-split on summary of one reduction returns summary
py26: remove dict comprehensions
nice import error around impyla installation
split on embarassing computations
remove pip signature around impyla import error
sql: clean summary on select
sql: cleaner By on summaries of selects
simplify dev build instructions
sql: clean by sql generation and column reordering on selects

http://stackoverflow.com/questions/25914329/rearrange-columns-in-sqlalchemy-select-object/25932733#25932733
sql: Clean projection on select using _raw_columns
sql: clean mixing of by and count(table)
Merge pull request #652 from mrocklin/sql-fixes-3

Even more SQL fixes