Property identify iTerm instead of just checking if MacOS is being used

adapter/__init__.py

@@ -20,9 +20,7 @@ def identify():
     if "TILIX_ID" in os.environ:
         return Tilix()
 
-    if sys.platform == "darwin":
-        # TODO: identify if we are actually using iTerm.
-        # This could be the stock terminal for all we know.
+    if os.environ.get("ITERM_PROFILE"):
         return ITerm()
 
     return NullAdapter()

adapter/implementations/NullAdapter.py

@@ -2,7 +2,7 @@ from adapter.base import TerminalAdapterInterface
 
 
 class NullAdapter(TerminalAdapterInterface):
-    err = "Terminal emulator not supported."
+    err = "This terminal emulator is not supported."
 
     def clear(self):
         print(self.err)