add support for setting global response headers using -header flag

add support for setting response headers for a successfuly triggered hook

README.md

@@ -1,4 +1,4 @@
-[![ghit.me](https://ghit.me/badge.svg?repo=adnanh/webhook)](https://ghit.me/repo/adnanh/webhook)[![Join the chat at https://gitter.im/adnanh/webhook](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/adnanh/webhook?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Flattr this](https://button.flattr.com/flattr-badge-large.png)](https://flattr.com/submit/auto?user_id=adnanh&url=https%3A%2F%2Fwww.github.com%2Fadnanh%2Fwebhook) 
+[![ghit.me](https://ghit.me/badge.svg?repo=adnanh/webhook)](https://ghit.me/repo/adnanh/webhook)[![Join the chat at https://gitter.im/adnanh/webhook](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/adnanh/webhook?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Flattr this](https://button.flattr.com/flattr-badge-large.png)](https://flattr.com/submit/auto?user_id=adnanh&url=https%3A%2F%2Fwww.github.com%2Fadnanh%2Fwebhook)
 
 # What is webhook?
 [webhook](https://github.com/adnanh/webhook/) is a lightweight configurable tool written in Go, that allows you to easily create HTTP endpoints (hooks) on your server, which you can use to execute configured commands. You can also pass data from the HTTP request (such as headers, payload or query variables) to your commands. [webhook](https://github.com/adnanh/webhook/) also allows you to specify rules which have to be satisfied in order for the hook to be triggered.
@@ -59,6 +59,9 @@ However, hook defined like that could pose a security threat to your system, bec
 # Using HTTPS
 [webhook](https://github.com/adnanh/webhook/) by default serves hooks using http. If you want [webhook](https://github.com/adnanh/webhook/) to serve secure content using https, you can use the `-secure` flag while starting [webhook](https://github.com/adnanh/webhook/). Files containing a certificate and matching private key for the server must be provided using the `-cert /path/to/cert.pem` and `-key /path/to/key.pem` flags. If the certificate is signed by a certificate authority, the cert file should be the concatenation of the server's certificate followed by the CA's certificate.
 
+# CORS Headers
+If you want to set CORS headers, you can use the `-header name=value` flag while starting [webhook](https://github.com/adnanh/webhook/) to set the appropriate CORS headers that will be returned with each response.
+
 # Interested in running webhook inside of a Docker container?
 Please read [this discussion](https://github.com/adnanh/webhook/issues/63).