Update README. Specify dependencies more clearly.

From: Fabian Pedregosa <fabian.pedregosa@inria.fr>

git-svn-id: https://scikit-learn.svn.sourceforge.net/svnroot/scikit-learn/trunk@351 22fbfee3-77ab-4535-9bad-27d1bd3bc7d8

README

@@ -23,11 +23,14 @@ below.
 Dependencies
 ===========
 
-To install this package, you will need python >= 2.5, NumPy, the
-Boost libraries and a working c++ compiler.
+The required dependencies to build the software are python >= 2.5,
+NumPy >= 1.1, SciPy, the Boost libraries and a working C++ compiler.
 
-In order to run the tests, you will need nosetests, python-dap
-(http://pypi.python.org/pypi/dap/) and sikits.optimization.
+Optional dependencies are scikits.optimization for module
+machine.manifold_learning.
+
+To run the tests you will also need nosetests and python-dap
+(http://pypi.python.org/pypi/dap/).
 
 
 Install
@@ -69,6 +72,7 @@ To check out the sources for subversion run the command::
 You can also browse the code online in the address
 http://scikit-learn.svn.sourceforge.net/viewvc/scikit-learn
 
+
 Bugs
 ----
 
@@ -77,7 +81,6 @@ requests to the tracker located at the address
 https://sourceforge.net/apps/trac/scikit-learn/report
 
 
-
 Testing
 -------