Base64 encode the signature string

Now that there are newlines in it, putting it in a header directly is awkward

Author: Ben Lavender

lib/chatops/controller.rb

@@ -102,7 +102,7 @@ def ensure_chatops_authenticated
       body = request.raw_post || ""
       signature_string = [@chatops_url, @chatops_nonce, @chatops_timestamp, body].join("\n")
       # We return this just to aid client debugging.
-      response.headers["Chatops-Signature-String"] = signature_string
+      response.headers["Chatops-Signature-String"] = Base64.strict_encode64(signature_string)
       raise ConfigurationError.new("You need to add a client's public key in .pem format via #{Chatops.public_key_env_var_name}") unless Chatops.public_key.present?
       if signature_valid?(Chatops.public_key, @chatops_signature, signature_string) ||
           signature_valid?(Chatops.alt_public_key, @chatops_signature, signature_string)

spec/lib/chatops/controller_spec.rb

@@ -77,7 +77,7 @@ def rails_flexible_post(path, outer_params, jsonrpc_params = nil)
     signature = Base64.encode64(@private_key.sign(digest, signature_string))
     request.headers["Chatops-Signature"] = "Signature keyid=foo,signature=#{signature}"
     get :list
-    expect(response.headers["Chatops-Signature-String"]).to eq signature_string
+    expect(response.headers["Chatops-Signature-String"]).to eq Base64.strict_encode64(signature_string)
     expect(response.status).to eq 200
     expect(response).to be_valid_json
   end