Add RavenHandler and RavenFormatter for working with Raven which is the
protocol used by Sentry (http://github.com/dcramer/sentry). Uses
raven-php (https://github.com/getsentry/raven-php).
composer.json: Tighten requirement "raven/raven": ">=0.2.0" to
"raven/raven": "0.2.*" as suggested by @Seldaek in
https://github.com/Seldaek/monolog/pull/76/files#r737288
Remove leading \ in use statement, as suggested by @Seldaek in
https://github.com/Seldaek/monolog/pull/76/files#r737290
Map CRITICAL and ALERT to ERROR because raven doesn't have more than
ERROR, because otherwise those messages will fail. As suggested by
@Seldaek in https://github.com/Seldaek/monolog/pull/76/files#r737292
Minor reformatting suggested by @Seldaek in
https://github.com/Seldaek/monolog/pull/76/files#r737297
Put braces on same line for if statements, as requested by @Seldaek in
https://github.com/Seldaek/monolog/pull/76/files#r737303
Put args one per line, as suggested by @Seldaek in
https://github.com/Seldaek/monolog/pull/76/files#r737313
Rework how exceptions are stored and accessed using suggestions from
@Seldaek in https://github.com/Seldaek/monolog/pull/76/files#r737312
Change check of record level to >= Logger::ERROR instead of >
Logger::ERROR, as suggested by @Seldaek in
https://github.com/Seldaek/monolog/pull/76#r737303
Eliminate local variables used as pseudo-named-arguments, as suggested
by @Stof in https://github.com/Seldaek/monolog/pull/76#r740449
Change key from 'context' to 'exception' in
RavenHandlerTest::testException
Pull MockRavenClient (which depends on Raven_Client) out of
tests/Monolog/Handler/RavenHandlerTest.php into a separate file so that
the test can pass when raven-php is installed and can be skipped when
raven-php is not installed. Addresses @Stof's comment in
https://github.com/Seldaek/monolog/pull/76#r740465
Curly braces on same line for try/catch, as suggested by @stof in
https://github.com/Seldaek/monolog/pull/76#r743295
Address a few of the concerns from @stof in #76.
Remove RavenFormatter; this is not needed since Raven is a very simple
text-oriented interface and doesn't need special processing.
Remove `close` method which was setting `$this->ravenClient = null`
Add note about RavenHandler to README.mdown
Merge remote-tracking branch 'msabramo/raven'

Conflicts:
	README.mdown
	composer.json
Update raven log level mappings
Update changelog