Ignore top-level hidden dirs/files by default

Rather than waiting for each contributor to attempt to submit
a change to .gitignore trying to add the $editor_of_the_week
hidden directory just to be rejected, let's just ignore hidden
files/dirs by default in the top-level neutron directory.

Change-Id: I145bec958a3db7423a4e820a310b138ed189d2cc

.gitignore

@@ -3,7 +3,6 @@ build/*
 build-stamp
 ChangeLog
 cover/
-.coverage
 covhtml/
 dist/
 doc/build
@@ -20,9 +19,13 @@ run_tests.err.log
 run_tests.log
 setuptools*.egg/
 subunit.log
-.testrepository
-.tox/
-.venv/
 *.mo
 *.sw?
 *~
+/.*
+!/.coveragerc
+!/.gitignore
+!/.gitreview
+!/.mailmap
+!/.pylintrc
+!/.testr.conf