fix minor README.md errors

[iekumdario]

Hello,

I was adding raygun support for a new logging library at work and came across these docs. There are some typos and outdated class and method names I found while reading how to use the library, and had to go and double check some info.

So I figured I might as well submit a pull request on the readme however minor. Please consider it.

Thanks

[comingupmilhouse]

Thanks @iekumdario. I will check your changes with the team today

[TheRealAgentK]

For some reason this only ever got partly addressed, sorry @iekumdario . Fixing the remaining issues in #94.