Add options

[tj-commits]

I think there should be another parameter/argument for options in the isNumber function because some people may not want isNumber to return true when a stringified number is passed in. Therefore the following options should be included in an optional options parameter/argument:

allowStrings: boolean // allow strings that are numbers like "1" to be considered numbers in isNumber()
allowInfiniteNumbers: boolean // allow numbers that are not finite because your library currently does an isFinite check which should be optional