Expose the clear/1 fun from counter in the folsom api

Conflicts:
	test/folsom_erlang_checks.erl
Merge pull request #46 from basho/rdb-counter-clear

Expose the clear/1 fun from counter in the folsom api
Merge pull request #47 from basho/jdb-faster-slide-eunit-fixes-squashed

Improve performance of slide histogram
Fix eunit folsom_erlang_checks test
Add a error tolerance notify method

If folsom_sup is crashed then folsom's ets tables are deleted. In this
case notify method raise the exception. I added error tolerance method
to reduce the folsom's influence to the application code.
Merge pull request #49 from avasenin/fix-eunit-tests

Fix eunit folsom_erlang_checks test
Merge pull request #50 from avasenin/safely-notify

Add a error tolerance notify method
Added grouped/tagged metrics feature
Fixed a small issue in grouped metrics unit tests
Added untag_metric/2 API call, updated unit tests accordingly, small improvements
Merge pull request #51 from AlexandreBeaulne/groupedmetrics

Added grouped metrics feature
Remove ineffective assertion in duration test.

Erlang's timer:sleep/1 is inaccurate enough on some systems to cause this clause
to regularly fail.
Merge pull request #52 from banjiewen/master

Remove ineffective assertion in duration test.
bump bear to 0.1.3
replace use of now() with os:timestamp()
Merge pull request #54 from tsloughter/master

replace use of now() with os:timestamp()
Change the order of delete cascade for `spiral'

A crash of `folsom_metrics_histogram_ets` leaves spirals broken.
The spiral ets table goes away, so it can not be updated, nor
can it be deleted and re-created due to the delete order of
metric table, spiral table, folsom table. Have changed the order
to be more like that of `histogram` so deletes will succeed in
the event of a missing `spiral` ets table.
Merge pull request #56 from basho/rdb-spiral-delete

Change the order of delete cascade for `spiral'
Let the slide server crash and stay crashed after multiple errors

The restart strategy on the slide server was such that it would
_never_ stop in the case that the ets table it was trimming went away.
Instead it would metronimically add a crash message to your log
every 30 seconds. This commit sets the restart strategy to 3
failures in 3 minutes. Since the only seen live examples of
a slide server crash have been when the ets table has gone
away, it is best crash and stay dead than be restarted after
3 failed trims.
Merge pull request #57 from basho/rdb-letitcrash

Let the slide server crash and stay crashed after multiple errors