udate dependencies and make examples work

[tyrchen]

It looks existing code cannot be compiled with rust 1.39. I tried to make it work and also updated dependencies to their latest version as much as possible.

It took me a while to make all the examples work. I might be wrong - however, I found that remove_ascii_armor may have two problems that I commented below.

Not sure if the coding style follows your standard, after all the changes I run cargo fmt against the whole codebase.

The code works with my own updates to the bpb, which I'd send a PR once this is accepted.