go: simplify

[LionNatsu]

Changes proposed in this pull request:

• go: simplify nested literals
• go: prune assignment of range for
• go: omit the high index

I used gofmt -s -w to do this work, and committed them separately.

It is okay for Go>=1.5, because these changes are compatible to the old version (at least 6 yrs ago) of Go specs (Go 1.0 is about 4 yrs ago). the commit in tree of Go that introduced these grammar are as follows:

• omitting type in nested literals golang/go@a12141e
• one index in range clause golang/go@30a1a8c#diff-fa1137b681c060dc28132cf2a9418a23R2648
• omitting high index golang/go@1a8ebcc#diff-94792ed6b8d17736ee79af0ca532d6feR2365

[coveralls]

Coverage remained the same at 90.475% when pulling 45a1952 on LionNatsu:patch-simplify into 66c871e on yuin:master.

[yuin]

Sorry, I prefer explicit code.