It's required because:
- go.mod file can contain comments
- easyjson should respect comments and be able to parse go.mod
This commit replaces the logic of parsing go.mod file with the original
one from golang.org/x/mod/modfile package. Tests have been
introduced to check the behavior of `getModulePath` function.
Ref:
- https://golang.org/cmd/go/#hdr-The_go_mod_file
Ivan Boyarkin