Throw exceptions from Varnish class (fix #11)

Note exception throwing on proxy interface

Add @throws tags
Removed obsolete setUp method

Bring PHPDocs in line with PSR-5
Implement log event subscriber and other improvements

Rename construction to setup

Fix use statement

Add unexpected collection to collection instead of throwing

Add MissingHostException explanation

Improve class description

Fix logger example

Re-add Monolog suggestion
Merge pull request #25 from ddeboer/exceptions

Throw and log exceptions