Use TypeScript and update immutable to version 4.0.0-rc.12

[nggonzalez]

Description

Modernize the library by adding Typescript and prettier, updating function names, creating smaller files, and updating dependencies.

Updates immutable to the latest version (4.0.0-rc.12) and adds an option for AnonymousRecords when the recordType is not found.

Changes

• Update Iterable.isIterable to the new isCollection method for determining if something is an immutable Collection (Map, Set, List, OrderedSet, OrderedMap, Stack)
• Update instanceof Record to Record.isRecord for checking if something is a Record
• Remove record.toMap() and use record.toSeq() to iterate through key/value pairs
• Add an option for throwOnMissingRecordType which defaults to true. When false, this option will enable the creation of AnonymousRecords that contain all of the data keys found in the initially decodedData.
• Remove babel
• Update ava dependency
• Add typescript and tsconfig
• Add tslint
• Add husky and lint-staged
• Export types

[nggonzalez]

@avocode Would appreciate your review when you get a chance

[nggonzalez]

Ping @avocode