Reduce front-page loading time

[ksurya]

The front-page of the site is taking lot of time than usually expected to load. The probably fixes for improving are

1. The page loads most-viewed, latest submissions, top tags, top authors features every time. These implementations can be improved to reduce database load.
2. Use cache (memcache) on the front-page.

References: scipy_central.submission.templatetags.core_tags