Fetch user/org repos from github

[maizy]

• fetching
  • pagination
  • open & private repo types
  • Link header parsing
  • fields parsing
  • parallel fetching support
  • custom User-Agent
  • request timeouts (may be set globally by ws.timeout, TODO: special settings for github client)
• force reload
• caching
  • refresh cache when app started (Refresh repositories cache when app starts and then periodically #31)
  • periodic refresh cache (Refresh repositories cache when app starts and then periodically #31)
• json resources according to api.md
• some unittests (Unittests for RepositoriesFetcher & Github client #32)

---

org:

https://api.github.com/orgs/{org}/repos?per_page=100&page={1, 2...}&type=private&type=open

user:

https://api.github.com/users/{org}/repos?per_page=100&page={1, 2...}&type=private&type=open

pagination header:

Link: <https://api.github.com/user/repos?page=3&per_page=100>; rel="next",
  <https://api.github.com/user/repos?page=50&per_page=100>; rel="last"