Panicked while calling peek on a empty PriorityQueue

[zonyitoo]

https://github.com/garro95/priority-queue/blob/master/src/pqueue.rs#L90

thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0', /Users/travis/build/rust-lang/rust/src/libcollections/vec.rs:1552

[garro95]

Fixed in crate version 0.3.1. Thanks for reporting