Speed up isBoolean.
Null checks aren't helpful in isUndefined.
Undefined checks aren't helpful in isNull.
Adding a NaN test to isNumber to match spec and current behavior.
String coercion is already automatic for "test", and regex conversion is automatic for "match".
Using ES5 Array#indexOf when available.
Using the cached hasOwnProperty everywhere.
Merge pull request #6 from ljharb/generic_improvements

Generic improvements