doc updates
minor edit
Merge branch 'master' of github.com:qos-ch/slf4j
added links to SLF4J-Test and Lidalia SLF4J Extensions projects
add link to beginner's tutorial
improved video link
improved link image
updated links
Fix BasicMarkerFactory by using ConcurrentMap

Problems fixed:
1. unsafe publication because of constructor lacks synchronized(this)
when assigning markerMap
2. detachMarker() lacks synchronization
Merge pull request #40 from ash2k/marker-synchronization

Fix BasicMarkerFactory by using ConcurrentMap
mention BasicMarkerFactory concunrrency improvement
Fix of Bug 279
http://bugzilla.slf4j.org/show_bug.cgi?id=279
Now P8 FileNet Content Manager can use log4j-over-slf4j instead of
log4j. See also
http://www-03.ibm.com/software/products/us/en/filecontmana/
Add readme and enable travis-ci
Don't truncate logger names when API_LEVEL >=7

The limitation of 23 characters doesn't apply on SDK >= 7.
File-based log level configuration

Loggable levels are no more checked using Log.isLoggable(level) but using
a configuration file named "slf4j.properties" and located in "assets"
folder.
Unit test Logger configuration retrieved through LoggerFactory