[skip ci] Mention curl-config in readme

Croydon · Croydon · commit f7192dff80a5 · 2018-09-26T07:42:47.000+02:00
diff --git a/README.md b/README.md
@@ -102,6 +102,11 @@ In Ubuntu:
 sudo apt-get install libssl-dev
 ```
 
+Additionally, you need `curl-config` on your system. You need one of these packages:
+  * libcurl4-gnutls-dev
+  * libcurl4-nss-dev
+  * libcurl4-openssl-dev 
+
 If you are still encountering problems while installing, you should try the
 [Building from source](http://www.nodegit.org/guides/install/from-source/)
 instructions.
