Avoid the call gocode during this condition

- Conditions
  - Hook the insert of dot(.)
  - Typed the package has not yet been imported use context['input']
  - Match the typed package name and json file name

Signed-off-by: Koichi Shiraishi <k@zchee.io>

- Add parses library name
  -  e.g. 'go/ast' is 'go'
  - If imported 'github.com/pkg/errors', ignore cache for 'errors'

- Change json cache files
  - 'go/ast' is '/path/to/go/ast.json'
  - 'errors' is '/path/to/errors/errors.json'

Signed-off-by: Koichi Shiraishi <k@zchee.io>