fix tab-space mixture issue in README

Author: ycjuan

README

@@ -332,13 +332,13 @@ to classify new data.
 
     For example, if we have the following training data:
 
-    LABEL	ATTR1	ATTR2	ATTR3	ATTR4	ATTR5
-    -----	-----	-----	-----	-----	-----
-      1		  0	  0.1	  0.2	  0	  0
-      2		  0	  0.1	  0.3	 -1.2	  0
-      1		  0.4	  0	  0	  0	  0
-      2		  0	  0.1	  0	  1.4	  0.5
-      3		 -0.1	 -0.2	  0.1	  1.1	  0.1
+    LABEL    ATTR1    ATTR2    ATTR3    ATTR4    ATTR5
+    -----    -----    -----    -----    -----    -----
+      1        0        0.1      0.2      0        0
+      2        0        0.1      0.3     -1.2      0
+      1        0.4      0        0        0        0
+      2        0        0.1      0        1.4      0.5
+      3       -0.1     -0.2      0.1      1.1      0.1
 
     then the components of svm_problem are:
 
@@ -347,10 +347,10 @@ to classify new data.
     y -> 1 2 1 2 3
 
     x -> [ ] -> (2,0.1) (3,0.2) (-1,?)
-	 [ ] -> (2,0.1) (3,0.3) (4,-1.2) (-1,?)
-	 [ ] -> (1,0.4) (-1,?)
-	 [ ] -> (2,0.1) (4,1.4) (5,0.5) (-1,?)
-	 [ ] -> (1,-0.1) (2,-0.2) (3,0.1) (4,1.1) (5,0.1) (-1,?)
+         [ ] -> (2,0.1) (3,0.3) (4,-1.2) (-1,?)
+         [ ] -> (1,0.4) (-1,?)
+         [ ] -> (2,0.1) (4,1.4) (5,0.5) (-1,?)
+         [ ] -> (1,-0.1) (2,-0.2) (3,0.1) (4,1.1) (5,0.1) (-1,?)
 
     where (index,value) is stored in the structure `svm_node':