Do not read temporary editor files, fixes #548

This fixes a bug where Terraform would error with the following:

```
Error loading config: Error reading
/Users/rhenrichs/work/example/.#example.tf: open
/Users/rhenrichs/work/example/.#example.tf: no such file or directory
```

The solution implemented here ignores the common emacs and vim
temporary file formats to fix the issue in question. It does so by
matching on the name of the file.

Note: the danger with merging this is that Terraform could quickly
have requests to ignore other file formats.