Pre-render index page

[SignpostMarv]

Improves further upon #2, possibly maxing out the page speed score & negating a rare bug that would occur due to the GitHub API rate limiting rules.

• moved the prettyDate() output from the header widget to the repo widgets to normalise heights of all widgets
• don't run prettyDate() on pre-render pass, increased margin to eliminate vertical repositioning of text
• pre-render with phantomjs via grunt-html-snapshot, using grunt-contrib-rename to overwrite index.html with pre-rendered content.
• run prettyDate() in output, displaying recent update info for all repos.
• remaining page speed improvements at time of writing relate to third-party APIs (i.e. speed score is not likely to improve any further)
• eliminates the rare scenario where no repos are listed due to rate-limiting on the GitHub API.

Comparisons:

• before - mobile speed score 89, desktop 95
• after - mobile speed score 96, dekstop 97

[mihai-vlc]

Since the hotness is not used anymore we should remove it.

[SignpostMarv]

removed it and related variables.

[SignpostMarv]

Updated as requested, no score changes

[mihai-vlc]

Looks nice, thank you !