Make readme less confusing regarding go modules

when the readme was written, go modules were still pretty new.
It therefore made sense to provide both versions of how to
add the dependency.

Since go modules have become pretty much the standard,
we do not have to keep both parts in the readme

README.md

@@ -12,20 +12,14 @@ Basically: this lib can probably read most Keepass2 files, but only Keepass v2.3
 Use `go get` to retrieve the latest version:
 
 ```
-go get -u github.com/tobischo/gokeepasslib
+go get -u github.com/tobischo/gokeepasslib/v3@latest
 ```
 
-Include it in an application (modulized):
+For including it in your code:
 ```
 import "github.com/tobischo/gokeepasslib/v3"
 ```
 
-For non-modulized applications use:
-```
-import "github.com/tobischo/gokeepasslib"
-```
-Note that this may cause breaking changes when updating from a previous version.
-
 ### Example: reading a file
 
 ```go