v0.1.0 - Add services

Support following services for fetch and byId

• carts
• categories
• channels
• comments
• customObjects
• customers
• customerGroups
• inventories
• orders
• products
• productTypes
• reviews
• shippingMethods
• taxCategories

# example

client = new SphereClient Config

client.products.fetch()
client.customers.byId('1234567890').fetch()