initial draft
build full WriteBatch in v8 thread
(uv_after_work_cb) cast in cbatch for Node 0.10
bring cbatch properly into the fold

style, checks, buffers, etc.
expand basic chained batch tests
test reusability & exception clarification & fixes
add 'name' argument back to LD_STRING_OR_BUFFER_TO_SLICE
missing namespace
modularise put-get-del-test
V8 upgrade requiring `isolate` argument
auto cleanup of open iterators on db.close()

closes #22
fix comment