Add the stdio backend

This patch adds the stdio backend which acts as a fallback backend and
uses standard input and output.  For password queries, the rpassword
crate is used to suppress output.  Also, default_backend is changed to
return Stdio if Dialog is not available.

1 files changed, 1 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 1a6c816..a4087a8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,3 +12,4 @@ readme = "README.md"
 license = "MIT"
 
 [dependencies]
+rpassword = "2"