DOC: Change mention of SVN to Git.

Author: rgommers

DEV_README.txt

@@ -3,7 +3,7 @@ available.
 
 We have a few simple rules: 
 
-   * try hard to keep the SVN repository in a buildable state and to not
+   * try hard to keep the Git repository in a buildable state and to not
      indiscriminately muck with what others have contributed.
 
    * Simple changes (including bug fixes) and obvious improvements are 
@@ -14,6 +14,6 @@ We have a few simple rules:
    * Please add meaningful comments when you check changes in.  These
      comments form the basis of the change-log.  
 
-   * Add unit tests to excercise new code, and regression tests
+   * Add unit tests to exercise new code, and regression tests
      whenever you fix a bug.