Ignore emacs lisp files (#297)

Tahoe-LAFS project has a file named `/misc/coding_tools/coverage.el`, which is often uploaded to codecov along with the regular coverage report.  I'm not sure it is doing any harm, but can't be doing anything useful either!

It would be nice if codecov could ignore `.el` files.

codecov/__init__.py

@@ -88,6 +88,7 @@ def sanitize_arg(replacement, arg):
     r"(/\.coverage.*)|"
     r"(\.coveragerc)|"
     r"(\.egg)|"
+    r"(\.el)|"
     r"(\.gif)|"
     r"(\.ini)|"
     r"(\.less)|"