Use reexported postgres for NoTls in examples

[dpetersen]

As we just discussed in #23. Rather than a big warning in the README about specific versions of the Postgres library which you'd have to remember to manually update, I just made the examples use the reexported library as you suggested.

I removed the use postgres::Client since that wasn't actually getting used in the example and was generating a warning.

[dpetersen]

It's weird that cargo test is failing on Circle, since I did run it and it's passing locally. Good to see my superpower of breaking CI still works on a Saturday.

[sfackler]

CI is running against 1.40, which I'd guess is too old for that version of subtle. It looks like you should just need to bump that to 1.41.0: https://github.com/dalek-cryptography/subtle/blob/master/.travis.yml#L16

[dpetersen]

Ah, that makes since. I installed 1.40.0 locally (rustup is awesome) and replicated the issue, then bumped locally. And immediately got this failure:

error[E0658]: use of unstable library feature 'matches_macro'                                                  
   --> /home/dpetersen/.cargo/registry/src/github.com-1ecc6299db9ec823/postgres-protocol-0.5.3/src/authentication/sasl.rs:333:29                                                                                              
    |                                                                                                          
333 |         self.take_while(|c| matches!(c, '\x21'..='\x2b' | '\x2d'..='\x7e'))                              
    |                             ^^^^^^^                                                                      
    |                                                                                                          
    = note: for more information, see https://github.com/rust-lang/rust/issues/65721                           

Looked that up and it was stabilized in 1.42, so bumped to that and we're green.

[sfackler]

Thanks!