Add more links to docs and examples (#8)

opentracing: handle case where parent span is nil (#6)

Add Dominik Honnef to contributors

Merge pull request #4 from vcabbage/logger-func

Replace NewFuncLogger with LoggerFunc

Merge pull request #3 from peterhellberg/formatting-and-linting

Fix some formatting and linting issues

Put the warning note about context in its own paragraph in the docs

Add information about requiring the use of the ___Context() calls of the sql package to be able to work

Rename instrumented-mysql to instrumented-sqlite in the sqlite example

Place examples in seperate package, change logging example to use sqlite3

Complete justLogging example

Add an example with just logging and no tracing

Expand examples a bit

Update godoc badge