[ANN] etran: added support of default function arguments

A new version of etran parse transforms has been released.

https://github.com/saleyn/etran

In this version a "defarg" parse transform is added to support default
function arguments.

Example:

test(A / 10, B / 20) ->
  A + B.


The code above is transformed to:

test()    -> test(10);
test(A)   -> test(A, 20);
test(A,B) -> A+B.


More examples taken from unit tests:

defarg_test() ->
 ?assertEqual(3,     a()),
 ?assertEqual(9,     a(7)),
 ?assertEqual(10,    a(6,4)),
 ?assertEqual(7.0,   c()),
 ?assertEqual(9,     d()),
 ?assertEqual(5,     d(abc, [1,2])),
 ok.


a(A / 1, B / 2) ->
 A+B.


c(A / (10*2-15), B / (64 / 32)) ->
 A + B.


d(A / undefined, B / []) ->
 length(atom_to_list(A)) + length(B).


Regards,

Serge