Log Message:
Updated miller to 5.1.0.

This is a relatively minor release of Miller, containing feature
requests and bugfixes while I've been working on the Windows port
(which is nearly complete).

Features:

    JSON arrays: as described here, Miller being a tabular data
    processor isn't well-position to handle arbitrary JSON. (See
    jq for that.) But as of 5.1.0, arrays are converted to maps
    with integer keys, which are then at least processable using
    Miller. Details are here. The short of it is that you now have
    three options for the main mlr executable:

--json-map-arrays-on-input    Convert JSON array indices to Miller
map keys. (This is the default.) --json-skip-arrays-on-input
Disregard JSON arrays.  --json-fatal-arrays-on-input  Raise a fatal
error when JSON arrays are encountered in the input.

This resolves #133.

    The new mlr fraction verb makes possible in a few keystrokes
    what was only possible before using two-pass DSL logic: here
    you can turn numerical values down a column into their
    fractional/percentage contribution to column totals, optionally
    grouped by other key columns.

    The DSL functions strptime and strftime now handle fractional
    seconds. For parsing, use %S format as always; for formatting,
    there are now %1S through %9S which allow you to configure a
    specified number of decimal places. The return value from
    strptime is now floating-point, not integer, which is a minor
    backward incompatibility not worth labeling this release as
    6.0.0. (You can work around this using int(strptime(...)).) The
    DSL functions gmt2sec and sec2gmt, which are keystroke-savers
    for strptime and strftime, are similarly modified, as is the
    sec2gmt verb. This resolves #125.

    A few nearly-standalone programs -- which do not have anything
    to do with record streams -- are packaged within the Miller.
    (For example, hex-dump, unhex, and show-line-endings commands.)
    These are described here.

    The stats1 and merge-fields verbs now support an antimode
    aggregator, in addition to the existing mode aggregator.

    The join verb now by default does not require sorted input,
    which is the more common use case. (Memory-parsimonious joins
    which require sorted input, while no longer the default, are
    available using -s.) This another minor backward incompatibility
    not worth making a 6.0.0 over. This resolves #134.

    mlr nest has a keystroke-saving --evar option for a common use
    case, namely, exploding a field by value across records.

Documentation:

    The DSL reference now has per-function descriptions.

    There is a new feature-counting example in the cookbook.

Bugfixes:

    mlr join -j -l was not functioning correctly. This resolves
    #136.

    JSON escapes on output (\t and so on) were incorrect. This
    resolves #135.