Updated README.md with correct dependencies.

Author: karya0

README.md

@@ -1,5 +1,29 @@
 # Building the Modules
 
+Mesos modules provide a way to easily extend inner workings of Mesos by creating
+and using shared libraries that are loaded on demand. Modules can be used to
+customize Mesos without having to recompiling/relinking for each specific use
+case. Modules can isolate external dependencies into separate libraries, thus
+resulting into a smaller Mesos core. Modules also make it easy to experiment
+with new features. For example, imagine loadable allocators that contain a VM
+(Lua, Python, …) which makes it possible to try out new allocator algorithms
+written in scripting languages without forcing those dependencies into the
+project. Finally, modules provide an easy way for third parties to easily extend
+Mesos without having to know all the internal details.
+
+For more details, please see
+[Mesos Modules](http://mesos.apache.org/documentation/latest/modules/).
+
+
+## Prerequisites
+
+Building Mesos modules requires system-wide installation of the following:
+
+1. google-protobuf
+2. glog
+3. boost
+4. picojson
+
 ## Build Mesos with some unbundled dependencies
 
 ### Preparing Mesos source code
@@ -8,33 +32,39 @@ standard release in the form of a tarball and extract it, or clone the git
 repository.
 
 Let us assume you did extract/clone
-the repo into `~/mesos`. Let us also assume that you build mesos in a subfolder
+the repository into `~/mesos`. Let us also assume that you build Mesos in a
+subdirectory
 called `build` (`~/mesos/build`).
 
-### Building and Install Mesos
+### Building and Installing Mesos
 Next, we need to configure and build Mesos.
 Due to the fact that modules will need to have access to a couple of libprocess
-dependencies, mesos itself should get built with unbundled dependencies to
+dependencies, Mesos itself should get built with unbundled dependencies to
 reduce chances of problems introduced by varying versions (libmesos vs. module
 library).
 
 We recommend using the following configure options:
 
 ```
-./configure --with-glog=/usr/local --with-protobuf=/usr/local --with-boost=/usr/local
+cd <mesos-source-tree>
+mkdir build
+cd build
+../configure --with-glog=/usr/local --with-protobuf=/usr/local --with-boost=/usr/local --prefix=$HOME/usr
 make
 make install
 ```
 
-## Build Mesos-Modules
+Note that the `--prefix=$HOME/usr` is required only if you don't want to do a system-wide Mesos installation.
+
+## Build Mesos Modules
 
 Once that is done, extract/clone the mesos-modules package. For the sake of this
 example, that could be in `~/mesos-modules`. Note that you should not put
 `mesos-modules` into the `mesos` folder.
 
 You may now run start building the modules.
 
-The configuration phase needs to know some details about your mesos installation
+The configuration phase needs to know some details about your Mesos installation
 location, hence the following are used:
 `--with-mesos=/path/to/mesos/installation`
 
@@ -47,3 +77,6 @@ make
 ```
 
 At this point, the Module libraries are ready in `/build/.libs`.
+
+## Using Mesos Modules
+See [Mesos Modules](http://mesos.apache.org/documentation/latest/modules/).