Qiang Luo

Support defaulting to zero minutes/hours/seconds

2

```rust extern crate chrono; use chrono::NaiveDateTime; fn main() { println!("{}:", 1); if let Err(e) = NaiveDateTime::parse_from_str("2019010101", "%Y%m%d%H") { println!("{}", e); } println!("{}:", 2); if let Err(e) = NaiveDateTime::parse_from_str("201901010100", "%Y%m%d%H%M") {...

As far as I know, classifier in sklearn supports non integer class such as string now, so we should handle non integer class.

Setting default annualization factor for all metrics is quite handy sometimes. Currently this can be achieved by setting ``` empyrical.stats.ANNUALIZATION_FACTORS['daily'] = 24*252 ``` Please consider add an API for this...

In [prefix/libc](https://wiki.gentoo.org/wiki/Prefix/libc), repos_conf in $EPREFIX/etc/layman/layman.cfg is missing EPREFIX. It should be like storage with EPREFIX added