Removed tabs from indentation

CONTRIBUTING.md

@@ -15,23 +15,23 @@ GitHub:
 
 2. Clone this copy to your local disk:
 
-	$ git clone [email protected]:YourLogin/scikit-learn.git
+          $ git clone [email protected]:YourLogin/scikit-learn.git
 
 3. Create a branch to hold your changes:
 
-	$ git checkout -b my-feature
+          $ git checkout -b my-feature
 
    and start making changes. Never work in the ``master`` branch!
 
 4. Work on this copy, on your computer, using Git to do the version
    control. When you're done editing, do:
 
-	$ git add modified_files
-	$ git commit
+          $ git add modified_files
+          $ git commit
 
    to record your changes in Git, then push them to GitHub with:
 
-	$ git push -u origin my-feature
+          $ git push -u origin my-feature
 
 Finally, go to the web page of the your fork of the scikit-learn repo,
 and click 'Pull request' to send your changes to the maintainers for
@@ -50,7 +50,7 @@ following rules before submitting a pull request:
 -  All other tests pass when everything is rebuilt from scratch. On
    Unix-like systems, check with (from the toplevel source folder):
 
-	$ make
+          $ make
 
 -  When adding additional functionality, provide at least one
    example script in the ``examples/`` folder. Have a look at other
@@ -73,8 +73,8 @@ tools:
 
 -  Code with a good unittest coverage (at least 80%), check with:
 
-	$ pip install nose coverage
-	$ nosetests --with-coverage path/to/tests_for_package
+          $ pip install nose coverage
+          $ nosetests --with-coverage path/to/tests_for_package
 
 -  No pyflakes warnings, check with:
 
@@ -83,13 +83,13 @@ tools:
 
 -  No PEP8 warnings, check with:
 
-	$ pip install pep8
-	$ pep8 path/to/module.py
+           $ pip install pep8
+           $ pep8 path/to/module.py
 
 -  AutoPEP8 can help you fix some of the easy redundant errors:
 
-	$ pip install autopep8
-	$ autopep8 path/to/pep8.py
+           $ pip install autopep8
+           $ autopep8 path/to/pep8.py
 
 Bonus points for contributions that include a performance analysis with
 a benchmark script and profiling output (please report on the mailing