Use == instead of "is" for equality testing (#431)

Identity check (`is`, `is not`) with certain literals (e.g. strings,
numbers) is not guaranteed by the language specification to work and
issue a warning starting with Python 3.8, e.g.:

> examples/browse.py:326: SyntaxWarning: "is" with a literal. Did you mean "=="?

1 files changed, 1 insertions, 1 deletions

diff --git a/examples/browse.py b/examples/browse.py
index 6c0eb37..39ac27a 100755
--- a/examples/browse.py
+++ b/examples/browse.py
@@ -323,7 +323,7 @@ def store_initial_cwd(name):
 def starts_expanded(name):
     """Return True if directory is a parent of initial cwd."""
 
-    if name is '/':
+    if name == '/':
         return True
 
     l = name.split(dir_sep())