support caching of static images/css/js

[ericdriggs]

Implement file based caching where if a request is made for a static resource which matches on filename, the static version is returned. (can have query param for no caching)

Use cases: should dramatically speed up and reduce s3 usage.
May initially hard-code files to cache and later implement polling on files in a configurable directory.

Candidate files for caching:

css
bootstrap.min.css
cucumber.css
font-awesome.min.css

fonts
glyphicons-halflings-regular.woff2
glyphicons-halflings-regular.woff
glyphicons-halflings-regular.ttf
glyphicons-halflings-regular.svg
glyphicons-halflings-regular.eot
fontawesome-webfont.woff2
fontawesome-webfont.woff
fontawesome-webfont.ttf
fontawesome-webfont.svg
fontawesome-webfont.eot
FontAwesome.otf

js
bootstrap.min.js
Chart.min.js
jquery.min.js
jquery.tablesorter.min.js
moment.min.js