Add host and source to Splunk-HEC module

[matthias2]

Module doesn't allow to easily update source and host when using raw endpoint. Adding them to the url allows for source and host to be updated for the raw endpoint.
#21

[georgestarcher]

Closing this here because I have moved onto new Project of https://github.com/georgestarcher/splunk_hec_aio However I believe I didn't have host and source there on URL either. I will make an issue for it.