Avoid profile.*Profile* stutter in API

This was a very nice package I've only been waiting to use...

For a potential v2, I suggest reducing the stutter in the API (as also mentioned in this [comment](https://github.com/pkg/profile/issues/31#issuecomment-330331455)):
```go
profile.Path
profile.CPU
profile.Mem
profile.Allocs
...
```