Added new DHTML select element
Validate providers after creating all providers

* Speeds up setup_providers a bit by using the optimization used in
  clear_providers: All providers are added first, then validated. This
  buys a little time for the first provider that was added to get started
  on its collection
* I tried to keep the setup functionality separate, but gave up.
validate/_do_stats_match are more opportunitic and less verbose

* validate runs _do_stats_match before initiating a refresh in case the stats
  are already matched
* _do_stats_match logging tweaked a little bit; the debug statements that were
  removed were distracting, but the actual stats match log line got promoted
  to INFO.
s/browser/sel/

`pytest_selenium == pytest.sel == sel`
Merge pull request #503 from psav/dhtml_select

Added new DHTML select element
Added observed field back in
Merge pull request #509 from psav/fix_jenkins

Added observed field back in
New 'uses' fixtures, which provide -k filter marks
Merge pull request #504 from seandst/fixture-marks

New 'uses' fixtures, which provide -k filter marks
print statements go to events log, bottle listener is quiet by default

* New pytest commandline option: `--event-testing-verbose-listener`,
  probably does what you think.
Merge pull request #508 from seandst/setup-providers-speedup

Setup providers speedup
register_event fixture hooked up to the uses_event_listener mark
setup_providers adds all provider before validation
Merge pull request #510 from seandst/no-event-prints

print statements go to events log, bottle listener is quiet by default
Merge pull request #511 from seandst/setup-providers-speedup

setup_providers adds all provider before validation
Bump marker fixture scopes to session
Merge pull request #512 from seandst/fixture-marks

Bump marker fixture scopes to session
detect_observed_field bails if an element isn't visible
Merge pull request #513 from seandst/observered-field-noelement

detect_observed_field bails if an element isn't visible