Added _is_root() Cross-platform way to check admin rights

http://stackoverflow.com/questions/1026431/cross-platform-way-to-check-admin-rights-in-a-python-script-under-windows

bash_kernel/install.py

@@ -22,6 +22,14 @@ def install_my_kernel_spec(user=True):
         print('Installing IPython kernel spec')
         install_kernel_spec(td, 'bash', user=user, replace=True)
 
+def _is_root():
+    """Cross-platform way to check admin rights"""
+    import ctypes, os
+    try:
+        return os.geteuid() == 0
+    except AttributeError:
+        return ctypes.windll.shell32.IsUserAnAdmin() != 0
+
 def main(argv=None):
     install_my_kernel_spec()