Fix slither-simil fasttext import

Author: elopez

slither/tools/similarity/model.py

@@ -2,9 +2,9 @@
 
 try:
     # pylint: disable=unused-import
-    from fastText import load_model
-    from fastText import train_unsupervised
+    from fasttext import load_model
+    from fasttext import train_unsupervised
 except ImportError:
-    print("ERROR: in order to use slither-simil, you need to install fastText 0.2.0:")
-    print("$ pip3 install https://github.com/facebookresearch/fastText/archive/0.2.0.zip --user\n")
+    print("ERROR: in order to use slither-simil, you need to install fasttext>=0.2.0:")
+    print("$ pip3 install fasttext --user\n")
     sys.exit(-1)