HTTP HandleFunc / HTTP client tracing simplified

[noctarius]

Created a simplified way (wrapper / adapter) to handle simple cases like HTTP server handler or HTTP client requests. Other possibilities like SQL, MQ or other things could follow.

[noctarius]

PR builder fails due to the fact it tries to resolve github.com/instana/golang-sensor from the current master instead from the commit :(

[pglombardo]

Thanks @noctarius! Can you add some documentation on how to use these? Then a pointer to the example app? Maybe on the front README and I'll copy/paste into a docs PR for the go page.

[noctarius]

done :)

[steveww]

There is a neater way IMHO to do the handler wrappers, see https://github.com/steveww/go-appd

The wrappers are at the end of appd.go

[noctarius]

added :)

[steveww]

Much neater :-)

[noctarius]

fixed it :)

[pglombardo]

Yay I'll test soon and merge - thanks!

[pglombardo]

Tested & looks great. Thanks @noctarius & @steveww!