Safer escapes in removeFromHosts

On VMware, the machine ID is not a GUID like with VirtualBox, but the full path to the `.vmx` file (e.g. `/Users/dzuelke/.../blah.vmx`). The `sed` call to remove `/etc/hosts` entries then fails due to syntax errors.

This change fixes the `sed` call by using a colon as the delimiter, and by escaping that delimiter (if that's not done, then it'll interpret ":" as the command due to the leading slash from the path).

Tested with VMware Fusion, and of course verified that nothing breaks with VirtualBox either :)