trait objects without an explicit `dyn` are deprecated

[AndyGauge]

--> src/error_chain.rs:525:35	525	fn extract_backtrace(e: &(::std::error::Error + Send + 'static))	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use dyn: dyn ::std::error::Error + Send + 'static

::: src/example_generated.rs:24:5	24	error_chain!{}	-------------- in this macro invocation

= note: `-D bare-trait-objects` implied by `-D warnings`

error: trait objects without an explicit dyn are deprecated