Generalised website title

* Changed website name in templates to {{ site_title }} tag
* Added context processor which provides settings.SITE_TITLE in every template
* Added SITE_TITLE constant to settings, to be overriden by local.py
Generalised social media links

* Github on frontpage now linked to GITHUB_PROFILE setting value
Merge pull request #3 from entrepreneurj/generalise_webiste

Generalise website :+1: