code style
add browser_debug and test_browser to makefile
fix karma.local
add bin/mongoose.debug.js
add doc.validateSync
delete Error.key from DocumentArray
mongoose browser demo (add validateSync)
add validateSyc tests
delete Error.key from DocumentArray from validateSync
build mongoose browser
add comments for ValidateSync
Merge pull request #2477 from archangel-irk/master

add validateSync and small improvements