Caching repositories and members after requesting them to the Github API

These changes implement a mechanism for caching the information of repositories and members of the NCIP organization, once they have been requested to the Github API. The information is cached in the browser "localStorage", and it is recorded with an associated date of its last modification. The last modification date is then used in subsequent requests to the Github API in the form of conditional requests (http://developer.github.com/v3/#conditional-requests), that will only download new information if the data has changed since the last recorded modification time. Github API conditional requests do not count against the Rate Limit, and therefore this current entire caching mechanism reduces the number of request to only two that count against the rate limit. Normally, unauthenticated requests have a rate limit of 60 queries per hour.