Add a factory for AgenDAV\Http\Client

Makes easier initializing an authenticated HTTP client
Change caldav_http_auth_method valid values

No more CURL* values. Now this setting accepts 'basic' and 'digest' values
Use new CalDAV client on login

AgenDAV should be broken at this point, sorry
Add travis-ci badge

Despite tests just cover a small fraction of AgenDAV, having the badge here will
encourage me (and contributors) to keep writing tests.
Rename CalDAV client class to Client (no more Client2)

This commit also cleans up the old CalDAV client
Start adapting calendar controller
Do not manually start the session

Symfony sessions don't need to be manually started
Use the new CalDAV client to update calendars
Fetch events from calendars using new CalDAV client
Specify the Content-Type header for each request
Add the first test for the CalDAV client
Add more tests for CalDAV client

Changed the testing approach by mocking Http Client
Test getCalendarHomeSet on CalDAV client
Fix fetchEventByUid() return value

Should return a single event
Fix event modification/dragging/resizing

Adapt to the new client and new Calendar objects.
Fix one more issue with event modification

I'm afraid all this code is disposable...
Remove ancient CalDAV CURLClient

Let's use the new client instead!
Merge branch 'feature/use_new_client' into develop
Merge branch 'develop' of github.com:adobo/agendav into develop