this introduces disk format v4
now the summary rows for a term are stored in their own
"dictionary row" format, previously the same information
was stored in special term frequency rows
this now allows us to easily iterate all the terms for a field
in sorted order (useful for many other fuzzy data structures)
at the top-level of bleve you can now browse terms within a field
using the following api on the Index interface:
FieldDict(field string) (index.FieldDict, error)
FieldDictRange(field string, startTerm []byte, endTerm []byte) (index.FieldDict, error)
FieldDictPrefix(field string, termPrefix []byte) (index.FieldDict, error)
fixes#127
now created through the index itself
mapping problems reported early at the time
data is added to the batch, previously these
were not reported until the batch was executed
now you can access the underlying index/store implementations
using the Advanced() method. this is intedned for advanced
usage only, and can lead to problems if misused.
also, there is a new method NewUsing(...) which allows callers
of the top-level API to choose which underlying k/v store they
want to use.
