Ignore spaces around commas (or at least after).

[pedrofurla]

pLam> [1, 2]
"parser" (line 1, column 4):
unexpected " "
expecting "[", digit, identifier, "\\" or "("
pLam> [1 , 2]
"parser" (line 1, column 4):
unexpected ","
expecting space, "[", digit, identifier, "\\" or "("
pLam> [1 ,2]
"parser" (line 1, column 4):
unexpected ","
expecting space, "[", digit, identifier, "\\" or "("

Surprisingly, spaces after [ are ok.

pLam> [ 1,2]
|> reductions count               : 0
|> uncurried β-normal form        : (λfl. (l (λfx. f x)) (λfl. (l (λfx. f (f x))) (λfl. f)))
|> curried (partial) α-equivalent : (λf. (λl. ((l 1) (λf. (λl. ((l 2) (λf. (λl. f))))))))

[pedrofurla]

PR Fixes #11