Additional constructor with reference to zuliprc (fix #7)

This constructor takes a file name as argument. The file name is used to
parse the zuliprc file.

Author: Markus Keunecke

src/main/java/io/taliox/zulip/ZulipRestExecutor.java

@@ -2,6 +2,14 @@
 
 import io.taliox.zulip.calls.ZulipRestAPICall;
 import io.taliox.zulip.controller.HttpController;
+import org.apache.commons.configuration2.INIConfiguration;
+import org.apache.commons.configuration2.SubnodeConfiguration;
+import org.apache.commons.configuration2.ex.ConfigurationException;
+
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.Reader;
 
 /**
  * The Class ZulipRestExecutor which is responsible for executing requests and
@@ -27,6 +35,31 @@ public ZulipRestExecutor(String userName, String password, String serverURL) {
 		this.httpController = new HttpController(userName, password, serverURL);
 	}
 
+	/**
+	 * A constructor for the Zulip REST API executor taking the file name of a zuliprc file. The information from the
+	 * file is used to configure the executor.
+	 * <br/>
+	 * An example that will be accepted:
+	 * [api]
+	 * email=some@mail.com
+	 * key=API_KEY
+	 * site=https://your.zulip.com
+	 * <br/>
+	 * The Executor is responsible for communicating with your Zulip server.
+	 * @param zuliprcFileName
+	 * 				Name of the zuliprc file which can be generated by a Zulip client.
+	 */
+	public ZulipRestExecutor(String zuliprcFileName) throws IOException, ConfigurationException {
+		INIConfiguration iniConfiguration = new INIConfiguration();
+        iniConfiguration.read(new FileReader(zuliprcFileName));
+		SubnodeConfiguration apiSection = iniConfiguration.getSection("api");
+		this.httpController = new HttpController(
+				apiSection.getString("email"),
+				apiSection.getString("key"),
+				apiSection.getString("site")
+		);
+	}
+
 	/**
 	 * Executes a HTTP call to a Zulip server.
 	 * 
@@ -38,4 +71,4 @@ public String executeCall(ZulipRestAPICall call) {
 		return call.execute(this);
 	}
 
-}
+}