Feature Request: Support encryption

The more we know about your system and use case, the more easily and likely we can help.

#### Environment info
* OS: N/A
* App Version (`Command/Ctrl + ,`): N/A

#### Description of the problem / feature request / question:

AFAIK, the secret gist means *not searchable* instead of *not accessible* by the public. I think it would be great to support encryption on the client side to make it really a secret, as such user could have less concern to the content they post.

#### If possible, provide a sample gist or screenshot:

#### If possible, provide the log files
- Mac: `~/Library/Application Support/Lepton/logs`
- Windows: `C:\Users\\AppData\Roaming\Lepton\logs`
- Linux: `~/.cached/Lepton/logs`
>The [debug mode](https://github.com/hackjutsu/Lepton/wiki) is recommended when producing the logs.
>You can send your log file to cosmo.lepton@gmail.com if don't want to post it here.