Index fixes/updates

* Fix rename! from Dictionary
* Make names!, rename!, and delete! to return the updated Index,
  rather than the names in the index
* Added tests for the above
Merge pull request #445 from JuliaStats/kms/index_update

RFC: Index fixes/updates
Merge pull request #443 from davidavdav/master

Added support for whitespace-delimited input to readtable()
Change summary to describe, closes #447
Merge pull request #450 from IainNZ/patch-2

Change summary to describe, closes #447
Deprecate vecbind, rbind, cbind
Allow C-style escapes in text input
Fix spelling mistake in error message
Add additional C-style escapes
Remove meaningless maximum file
Merge pull request #453 from garborg/deprecatebinds

Deprecate vecbind, rbind, cbind
Save some memory when constructing DataFrame
Merge pull request #454 from JuliaStats/allowescapes

Allow C-style escapes in text input
showall produces readable tables with many columns
Refactor DataFrame printing code
Merge pull request #459 from JuliaStats/showall

showall produces readable tables with many columns
Bug fixes and draft tests
Add specs
Correctly show() empty DataFrames
generate_column_names -> gennames