Add .idea and .iml to .gitignore (#1764)

.gitignore

 # Two-trick pony for OSX and other case insensitive file systems:
 # Ignore ./python binary on Unix but still look into ./Python/ directory.
+.idea/
 /python
 !/Python/
 *.cover
+*.iml
 *.o
 *.orig
 *.pyc