doc: "Troubleshooting" section + minor changes

docs/codesnippets/194_top_x_of_user.py

@@ -0,0 +1,15 @@
+from itertools import islice
+from math import ceil
+
+from instaloader import Instaloader, Profile
+
+PROFILE = ...        # profile to download from
+X_percentage = 10    # percentage of posts that should be downloaded
+
+L = Instaloader()
+
+profile = Profile.from_username(L.context, PROFILE)
+posts_sorted_by_likes = sorted(profile.get_posts(), key = lambda p: p.likes + p.comments)
+
+for post in islice(posts_sorted_by_likes, ceil(profile.mediacount * X_percentage / 100)):
+    L.download_post(post, PROFILE)

docs/codesnippets/92_import_firefox_session.py

@@ -0,0 +1,23 @@
+from glob import glob
+from os.path import expanduser
+from sqlite3 import connect
+
+from instaloader import ConnectionException, Instaloader
+
+# FIREFOXCOOKIEFILE = "/home/alex/.mozilla/firefox/l96w6b90.default/cookies.sqlite"
+FIREFOXCOOKIEFILE = glob(expanduser("~/.mozilla/firefox/*.default/cookies.sqlite"))[0]
+
+instaloader = Instaloader(max_connection_attempts=1)
+instaloader.context._session.cookies.update(connect(FIREFOXCOOKIEFILE)
+                                            .execute("SELECT name, value FROM moz_cookies "
+                                                     "WHERE baseDomain='instagram.com'"))
+
+try:
+    username = instaloader.test_login()
+    if not username:
+        raise ConnectionException()
+except ConnectionException:
+    raise SystemExit("Cookie import failed. Are you logged in successfully in Firefox?")
+
+instaloader.context.username = username
+instaloader.save_session_to_file()