remove redundant brackets from function signatures

Since "*" indicates zero or more occurrences, asterisk-prefixed args
needn't be marked optional (via "[...]").
add regexp flag order test for _.isEqual
add missing dev dependencies
Merge pull request #1443 from davidchambers/dev-dependencies

add missing dev dependencies
Merge pull request #1439 from davidchambers/signatures

remove redundant brackets from function signatures
Merge pull request #1441 from davidchambers/regexp-flag-order

add regexp flag order test for _.isEqual