feat: out-of-box experience (#2)

Reviewed-on: https://git.reya.su/reya/signed/pulls/2

crates/utils/src/lib.rs

@@ -0,0 +1,5 @@
+mod pubkey;
+mod time;
+
+pub use pubkey::shorten_pubkey;
+pub use time::{relative_time, relative_time_secs};