So, the new pattern is as follow:

• each module defines a module::Error type automagically implementing the std::error::Error trait thanks to the thiserror crate ;

• it may also define a new type module::Result<T> as syntactic sugar for std::result::Result<T, Error> ;

• potentially fallible functions returns Result<T> instead of T, of which the program using rust-bio can do whatever pleases it.

Does that please everyone? If so, I'll get on replacing the expect there and there with this.

Coverage increased (+0.04%) to 86.874% when pulling 98bce6f on delehef:thiserror into 480872e on rust-bio:master.

huge work !