Test for prettier datetime truncate repr
Implement prettier datetime truncate repr
Validate truncate arguments in a more informative way
PEP8-ify
Merge pull request #897 from cpcloud/datetime-truncate-repr

Prettier datetime truncate repr
Implement first/last reductions
Make first and last functions
xfail on last because negative slicing is not well supported in python
No need for SingleElementSlice anymore
Break out reductions to a single function
Implement slice for pytables Column
Add first and last to reduction test
Failing reduction on slices
Change reductions to use schema instead of _dtype
Add reduction usage test for first/last
Assume we have toolz latest
Make our reduction schema always be a datashape
Keep symbol
Remove first and last functions
Define str instead of repr