Give a more verbose gzip example

I misread the line on `GZIP_COMPRESSION_TYPE` to mean that **only** the listed mime types was allowed. 

This PR is meant to make the example more explicit.

Author: johanforssell

README.md

@@ -212,7 +212,7 @@ Settings here can overwrite the settings in HAProxy, which are only applied to t
 |EXTRA_ROUTE_SETTINGS|a string which is append to the each backend route after the health check,possible value: "send-proxy"|
 |EXTRA_SETTINGS|comma-separated string of extra settings, and each part will be appended to either related backend section or listen session in the configuration file. To escape comma, use `\,`. Possible value: `balance source`|
 |FORCE_SSL|if set(any value) together with ssl termination enabled. HAProxy will redirect HTTP request to HTTPS request.
-|GZIP_COMPRESSION_TYPE|enable gzip compression. The value of this envvar is a list of MIME types that will be compressed, possible value: `text/html text/plain text/css`|
+|GZIP_COMPRESSION_TYPE|enable gzip compression. The value of this envvar is a list of MIME types that will be compressed. Some possible values: `text/html text/plain text/css application/javascript`. See:[HAProxy:compression](http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#4-compression)|
 |HEALTH_CHECK|set health check on each backend route, possible value: "check inter 2000 rise 2 fall 3". See:[HAProxy:check](https://cbonte.github.io/haproxy-dconv/configuration-1.5.html#5.2-check)|
 |HSTS_MAX_AGE|enable HSTS. It is an integer representing the max age of HSTS in seconds, possible value: `31536000`|
 |HTTP_CHECK|enable HTTP protocol to check on the servers health, possible value: "OPTIONS * HTTP/1.1\r\nHost:\ www". See:[HAProxy:httpchk](https://cbonte.github.io/haproxy-dconv/configuration-1.5.html#4-option%20httpchk)|