Allow overriding the HTTP server URL for cases where a proxy is being used.
Add support for crash analysis when running with Firefox.
Merge pull request #13 from w3c/jgraham/http_server_override

Allow overriding the HTTP server URL for cases where a proxy is being used
fixup! Add support for crash analysis when running with Firefox.
fixup! Add support for crash analysis when running with Firefox.
Merge pull request #15 from w3c/jgraham/crash_detection

Add support for crash analysis when running with Firefox.
Allow symbols_path to be a url