Correct "DNS" to "DSN"

I alway get tripped up by this too. Fingers.
Test Go 1.2 on Travis
Merge pull request #3 from teslaworksumn/silly-doc-fix

Correct "DNS" to "DSN"
Add Sentry io.Writer
Merge pull request #5 from teslaworksumn/logging-integration

Add Sentry io.Writer for integration with standard logging platform
travis: Add race and coverage tests
Merge branch 'master' into convenience
Fixes to Writer for a clean merge