Typecheck predicate functions for enjoy.js

This is a collection of type checkers. It also checks for some types that only exist in enjoy.js projects, but it's useful even for non-enjoy projects as well.

The following general type checkers are part of the module:

• isArgumentsObject(a): Checks if a is an arguments object.
• isArray(a): Checks if a is a real array.
• isArrayLike(a): Checks if a is iterable like an array, e.g. a DOMElement or Arguments.
• isBoolean(a): Checks if a is a boolean.
• isChar(a): Checks if a is a string containing only one character.
• isCollection(a): Checks if a is a collection of values (array or object).
• isDate(a): Checks if a is a Date object.
• isError(a): Checks if a is an Error object.
• isFiniteNumber(a): Checks if a is an actual number (not NaN or +/-Infinity).
• isFloat(a): Checks if a is a real number (but not an integer).
• isFunction(a): Checks if a is a function.
• isInfiniteNumber(a): Checks if a is an infinite number like NaN or Infinity.
• isInfinity(a): Checks if a is positive or negative infinity.
• isInteger(a): Checks if a is an integer.
• isMathObject(a): Checks if a is the JavaScript built-in Math object.
• isNegativeInfinity(a): Checks if a is -Infinity.
• isNull(a): Checks if a is null.
• isNumber(a): Checks if a is a number (including NaN or +/-Infinity).
• isPositiveInfinity(a): Checks if a is Infinity.
• isPrimitive(a): Checks if a is a primitive type (everything but an object/array).
• isRegExp(a): Checks if a is a regular expression object.
• isString(a): Checks if a is a string.
• isUndefined(a): Checks if a is undefined.

The module also contains these enjoy-specific type checkers:

• isDerivable(a): Checks if a is an enjoy.js derivable object.
• isMethod(a): Checks if a is an enjoy.js multimethod.
• isType(a): Checks if a is an enjoy.js type object.