Set Accept header to application/json

Scryfall has requested that clients set the Accept header. Lets do that
to avoid getting blocked.

Fixes #32

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
-## 0.6.0
+## 0.6.1
+* Set Accept header to application/json
 
+## 0.6.0
 * Add version to User-Agent header
 * Add WithUserAgent option to enable customization of the User-Agent header

scryfall.go

@@ -16,7 +16,7 @@ import (
 )
 
 const (
-	Version = "0.6.0"
+	Version = "0.6.1"
 
 	defaultBaseURL      = "https://api.scryfall.com"
 	defaultUserAgent    = "go-scryfall/" + Version
@@ -223,6 +223,8 @@ func NewClient(options ...ClientOption) (*Client, error) {
 
 func (c *Client) doReq(ctx context.Context, req *http.Request, respBody interface{}) error {
 	req.Header.Set("User-Agent", c.userAgent)
+	req.Header.Set("Accept", "application/json")
+
 	if len(c.authorization) != 0 {
 		req.Header.Set("Authorization", c.authorization)
 	}