Improves readme installation instructions. Fixes #260.

readme.markdown

@@ -8,11 +8,8 @@ Interested in learning **how to create a package**? Skip directly to that sectio
 
 ## Contents
 
+- [Requirements](#requirements)
 - [Installation](#installation)
-	- [Unix](#unix)
-	- [Windows](#windows)
-		- [Using the pre-built archives](#using-the-pre-built-archives)
-		- [From source](#from-source)
 - [Nimble's folder structure and packages](#nimbles-folder-structure-and-packages)
 - [Nimble usage](#nimble-usage)
 	- [nimble refresh](#nimble-refresh)
@@ -47,15 +44,7 @@ Interested in learning **how to create a package**? Skip directly to that sectio
 - [Contribution](#contribution)
 - [About](#about)
 
-## Installation
+## Requirements
-
-The latest version of Nimble (in the master branch) is primarily tested with
-the latest version of the Nim compiler (in the devel branch). You can be sure
-that Nimble will compile with that version of the compiler (a green travis
-build status is also a good sign that this is the case).
-
-The latest version of Nimble (0.7.4) requires a version of Nim greater than
-or equal to 0.13.0. That being said, the latest version of Nim is recommended.
 
 Nimble has some runtime dependencies on external tools, these tools are
 used to download Nimble packages.
@@ -71,22 +60,42 @@ If the version is less recent than 1.9.0 then Nimble may have trouble using it.
 See [this issue](https://github.com/nim-lang/nimble/issues/105) for more
 info.
 
-The following sections give platform-specific instructions on how to
+## Installation
-compile and install Nimble.
 
-### Source based installation
+Nimble is now bundled with [Nim](http://nim-lang.org)
+(since Nim version 0.15.0).
+This means that you should have Nimble installed already, as long as you have
+the latest version of Nim installed as well. Because of this **you likely do
+not need to install Nimble manually**.
 
-Run this command in your **Nim** directory::
+But in case you still want to install Nimble manually, you can follow the
+following instructions.
 
+There are two ways to install Nimble manually. The first is using the
+``install_nimble.nims`` script included in the Nim distribution and
+[repository](https://github.com/nim-lang/Nim/blob/devel/install_nimble.nims).
+Simply execute this to install Nimble.
+
+```
 nim e install_nimble.nims
+```
 
-This assumes that you also used the source based installation and added
+This will clone the Nimble repository, compile Nimble and copy it into
-``$nim/bin`` to your ``PATH``. If you create a symlink to ``nim`` instead,
+Nim's bin directory.
-you also need to create a symlink for ``nimble``.
 
-### Windows
+The second approach is to install Nimble as a Nimble package. You can do this
+by compiling Nimble, then running ``nimble install`` in Nimble's directory.
 
-The Windows installer ships with ``nimble.exe`` out of the box.
+```
+git clone https://github.com/nim-lang/nimble.git
+cd nimble
+nim c src/nimble
+src/nimble install
+```
+
+**Note for Windows users**: You will need to rename ``nimble.exe`` after
+compilation to something else like ``nimble1.exe``, then run
+``src\nimble1.exe install``.
 
 ## Nimble's folder structure and packages