Fix timestamp parsing
Fix timestamp parsing

Due to the recent regression [1] on crates.io timestamps do not have
timezone information anymore. The fix is to try first to parse timestamp
assuming there is a timezone data. If not it fails back to parsing naive
timestamp with timezone (assuming the timestamp represents UTC)

[1] https://github.com/rust-lang/crates.io/issues/1123

Closes #20

imp/cargo-info