Add options to disable default features for zip and reqwest and enable rustls-tls for reqwest

[dkter]

Alternative to #153. Shouldn't change anything by default, but will allow a Rust-only build by disabling some default features:

gtfs-structures = { version = "0.41.2", default-features=false, features=["read-url", "reqwest-rustls-tls" ] }

[lolpro11]

By the way, bzip2 in the zip crate is rust only - it only needs the bzip2 lib during build, so it is safe to keep in.
zip-rs/zip-old#367