Keyringrs

- cli binary moved to examples.
- osx now uses `security-framework` library instead of cli.
- hex dependency removed on osx.
- update to `secret-service` for linux, which
- removes gmp as a dependency
- updates rust-crypto to RustCrypto
- correctly encrypts/decrypts blank input
- tests moved to `lib.rs`

Plan to move to 1.0 if this version is stable.

- bug fix for special characters on osx.

- fix behavior in windows where third-party editing of password would result in malformed retrieved password. The solution was to convert all strings to and from Windows utf16, where before I was passing the secret as a blob from utf8.
- remove dependency on rustcserialize, use hex.
- update rpassword to 2.0, removing dependency on termios
- fix some mistakes in syntax for targeting dependencies to an os.

- remove some unwraps which were causing a problem in linux

- bumped secret-service to 0.4.0, which improved error-handling around emptyr passwords a bit more (in 0.3.1), and made gmp dependency optional in 0.4.0

- yanked. But originally was trying to handle secret-service empty password better. But there was an error in secret-service 0.3