Update .gitmodules (#43)

Since GitHub is disabling unencrypted git I'm changing the url to support the change.

Author: LizardLad

.gitmodules

@@ -1,4 +1,4 @@
 [submodule "docs/build/html"]
 	path = docs/build/html
-	url = git://github.com/andrew-d/python-multipart.git
+	url = https://github.com/andrew-d/python-multipart.git
 	branch = gh-pages