Add UserSearchResult
Add GitHub#search_users
Test GitHub#search_users
Add github3.search_users

- Also added links for text matching for user search
Test github3.search_users
Merge branch 'feature-new-search-api' into feature-users-search

Conflicts:
	github3/github.py
	github3/search/__init__.py
	tests/integration/test_api.py
	tests/integration/test_github.py