package.json: Add test-cov to preversion
package.json: Add test-cov to preversion

Both to ensure the released package passes lint+test on the local
machine and so that .nyc_output is up to date for coverage checks.

Also move coverage checks directly after test-cov, since they are
fast/local and should be addressed early in any fix order.

Signed-off-by: Kevin Locke <ffb4761cba839470133bee36aeb139f58d7dbaa9@kevinlocke.name>

kevinoid/node-project-template,kevinoid/travis-status,kevinoid/travis-status,kevinoid/appveyor-status,kevinoid/stream-compare,kevinoid/stream-compare,kevinoid/node-project-template,kevinoid/swagger-spec-validator,kevinoid/git-branch-is,kevinoid/promised-read,kevinoid/appveyor-status,kevinoid/promised-read,kevinoid/git-branch-is,kevinoid/travis-status,kevinoid/node-project-template,kevinoid/swagger-spec-validator,kevinoid/swagger-spec-validator,kevinoid/git-branch-is,kevinoid/stream-compare,kevinoid/promised-read,kevinoid/appveyor-status