Fix `with-meta` for dcpaths.
Implement `pr/count` in terms of `r/fold`.
Fix busted `pr/distinct-by`.
Coerce `dseq/move!` dst-path to a Hadoop `Path`.
Add and use reducers version of `concat`.
Correctly `reduce-by` empty collections.
Use `nil`-out trick on missed multimethods.
Retry failing job-status polls with exponential backoff.
NLineInputFormat dseq default source shape is `:vals`.
Update dependency matrix.
Also ignore `Error`s during namespace loading.

Attempting to load all namespaces which were loaded client-side will
occasionally generate `Error`s we can safely ignore, such as
`ExceptionInInitializerError`.  Rather than attempt to enumerate all
known such “safe” `Error`s, just log and continue on all `Throwable`s
during initial namespace load.
Bring NEWS up-to-date with post-0.6.0 changes.
Release version 0.6.1.
Begin work on next iteration.