Fix installation tutorial links (#526)

* Fix installation link.

Signed-off-by: Carlos Agüero <caguero@openrobotics.org>

tutorials/01_intro.md

@@ -6,19 +6,22 @@ Next Tutorial: \ref installation
 
 Gazebo Transport is an open source communication library that allows sharing
 data between clients. In our context, a client is called a node. Nodes might
-be running within the same process on the same machine or on separate machines located
-around the world. Gazebo Transport is multi-platform (Linux, Mac OS X, and
-Windows), so all the low level details, such as data alignment or endianness, are
-hidden for you.
+be running within the same process on the same machine or on separate machines
+located around the world. Gazebo Transport is multi-platform (Linux, Mac OS X,
+and Windows), so all the low level details, such as data alignment or
+endianness, are hidden for you.
 
-Gazebo Transport uses [Google Protocol buffers]
-(https://developers.google.com/protocol-buffers/?hl=en) as the data type for
-communicating between nodes. Users can define their own messages using the
-Protobuf utils, and then exchange them between the nodes. Gazebo Transport
-discovers, serializes and delivers messages to the destinations using a
-combination of custom code and [ZeroMQ] (http://zeromq.org/).
+Gazebo Transport uses
+[Google Protocol buffers](https://developers.google.com/protocol-buffers/?hl=en)
+as the data type for communicating between nodes. Users can define their own
+messages using the Protobuf utils, and then exchange them between the nodes.
+Gazebo Transport discovers, serializes and delivers messages to the
+destinations using a combination of custom code and
+[ZeroMQ](http://zeromq.org/).
 
 ## What programming language can I use with Gazebo Transport?
 
-C++ is the native implementation and the only language that has all available library features.
-Python implementation is a wrapper around C++ methods using `pybind11`. It does not support all features like C++, but contains the main features such as publication, subscription and service request.
+C++ is the native implementation and the only language that has all available
+library features. Python implementation is a wrapper around C++ methods using
+`pybind11`. It does not support all features like C++, but contains the main
+features such as publication, subscription and service request.