Between 'map-literals.go' and 'map-literals-continued.go' there are four
changes (omit element type, single line the block, add space to align
the "Google" element, and remove the terminal comma in the block) which
makes it hard for reader a to understand what it is "you can omit" in the
'Map literals continued' section of 'moretypes.article'.

To avoid the three text changes that the article does not talk about,
update the before code in 'map-literals.go' to already be formatted on a
single line per map entry.

Also add code examples in the article explaining the two versions and
why the literal element type may be elided.

Fixes golang/tour#1449

Between 'map-literals.go' and 'map-literals-continued.go' there are four
changes (omit element type, single line the block, add space to align
the "Google" element, and remove the terminal comma in the block) which
makes it hard for a reader to understand what it is "you can omit" in
the 'Map literals continued' section of 'moretypes.article'.

To avoid the three text changes that the article does not talk about,
update the before code in 'map-literals.go' to already be formatted on a
single line per map entry.

Add code examples in the article explaining the two versions and why the
literal element type may be elided.

Fixes golang/tour#1449