Update timezone to be of float type (#24)

* Update timezone to be of float type

Reference: https://developers.facebook.com/docs/graph-api/reference/user
Fixes #23

* Update README

README.md

@@ -15,6 +15,7 @@ This is a Go library for making bots to be used on Facebook messenger. It is bui
 `paked/messenger` is a pretty stable library however, changes will be made which might break backwards compatibility. For the convenience of its users, these are documented here.
 
 
+- [23/1/17](https://github.com/paked/messenger/commit/1145fe35249f8ce14d3c0a52544e4a4babdc15a4): Updating timezone type to `float64` in profile struct
 - [12/9/16](https://github.com/paked/messenger/commit/47f193fc858e2d710c061e88b12dbd804a399e57): Removing unused parameter `text string` from function `(r *Response) GenericTemplate`.
 - [20/5/16](https://github.com/paked/messenger/commit/1dc4bcc67dec50e2f58436ffbc7d61ca9da5b943): Leaving the `WebhookURL` field blank in `Options` will yield a URL of "/" instead of a panic.
 - [4/5/16](https://github.com/paked/messenger/commit/eb0e72a5dcd3bfaffcfe88dced6d6ac5247f9da1): The URL to use for the webhook is changable in the `Options` struct. 

profile.go

@@ -6,6 +6,6 @@ type Profile struct {
 	LastName      string  `json:"last_name"`
 	ProfilePicURL string  `json:"profile_pic"`
 	Locale        string  `json:"locale"`
-	Timezone      int    `json:"timezone"`
+	Timezone      float64 `json:"timezone"`
 	Gender        string  `json:"gender"`
 }