Feature: client endpoint

[icyleaf]

Usages:

Quick shot

Halite.endpoint("https://httpbin.org").get("/get")

Use endpoint as configuration

client  = Halite::Client.new(endpoint: "https://httpbin.org")
# Or
client  = Halite::Client.new do
  endpoint "https://httpbin.org"
end

client.get("/get")

Overwrite the path of endpoint

client  = Halite::Client.new do
  endpoint "https://example.com/api"
end

client.get("users")      # GET https://example.com/api/users
client.get("/users")     # GET https://example.com/users

/relates #64