Set pcap name for each NetTest.
Add details about why we use Tor Hidden Services for reporting

Related to: https://github.com/TheTorProject/ooni-probe/issues/107
Update the README.md with bridge instructions.
Add obfsproxy_binary option to sample config
Merge pull request #127 from aagbsn/feature/document_how_ooni_uses_bridges

Feature/document how ooni uses bridges
Merge pull request #126 from hellais/docs/tor-hs-motivations

Add details about why we use Tor Hidden Services for reporting
Fix reference to global_options
Fix method generatePcapFilename
Check for root once at startup
Merge pull request #130 from aagbsn/fix/set_pcap_name_per_nettest

Fix/set pcap name per nettest
Merge pull request #129 from aagbsn/fix/add_obfsproxy_binary_option_to_sample_config

Add obfsproxy_binary option to sample config