Merge pull request #456 from mrocklin/boolean-fixes

expr: boolean fixes
into: error message
into: list <- dict_items (python 3)
Merge pull request #457 from mrocklin/bcolz2

Add BColz and chunking backend
Merge branch 'master' of github.com:ContinuumIO/blaze

Conflicts:
	blaze/api/into.py
remove old assertions about bokeh's presence
into: ColumnDataSource <- list, numpy, dynd, pandas, bcolz