JSON output, checkstyle compatible

[client9]

interestingly gometalinter emits a JSON array. as per https://github.com/koalaman/shellcheck/blob/master/shellcheck.1.md#user-content-formats

I would have expected 1-object-per-line style, but so be it.

(line breaks added for clarity)

[
 {
"linter":"misspell",
"severity":"warning",
"path":"words.go",
"line":83922,
"col":2,
"message":"\"mkea\" is a misspelling of \"make\""
}
]