Move assets/ to live under static/.

This decreases the clutter in the root directory of the Zulip
repository.

.gitattributes

@@ -1,7 +1,7 @@
 .gitignore export-ignore
 .gitattributes export-ignore
 /analytics export-ignore
-/assets export-ignore
+/static/assets export-ignore
 /bots export-ignore
 /corporate export-ignore
 /static export-ignore

docs/directory-structure.md

@@ -58,7 +58,7 @@ templating systems.
 
 * `node_modules/` Third-party JavaScript installed via `npm`.
 
-* `assets/` For assets not to be served to the web (e.g. the system to
+* `static/assets/` For assets not to be served to the web (e.g. the system to
                    generate our favicons).
 
 -----------------------------------------------------------------------

tools/setup/emoji_dump/build_emoji

@@ -6,4 +6,4 @@ rm -rf static/third/gemoji/images
 (cd tools/setup/emoji_dump && python ./emoji_dump.py)
 mkdir -p static/third/gemoji/images
 mv tools/setup/emoji_dump/out static/third/gemoji/images/emoji
-cp -RPp assets/zulip-emoji/* static/third/gemoji/images/emoji/
+cp -RPp static/assets/zulip-emoji/* static/third/gemoji/images/emoji/

tools/update-prod-static

@@ -44,7 +44,7 @@ subprocess.check_call(['bash', '-ex', 'tools/setup/download-zxcvbn'],
                       stdout=fp, stderr=fp)
 
 # Collect the files that we're going to serve.
-subprocess.check_call(['python', './manage.py', 'collectstatic', '--noinput'],
+subprocess.check_call(['python', './manage.py', 'collectstatic', '--noinput', '-i', 'assets'],
                       stdout=fp, stderr=fp)
 
 # Compile translation strings to generate `.mo` files.