Allow creating a Term from an arbitrary Read/Write pair.

[stuhood]

Fixes #34. Method and struct names are eminently bikesheddable.

Unfortunately there are some public API changes necessary: described inline.

[stuhood]

The derivation of Copy just isn't possible in a safe way for arbitrary Read/Write destinations. And allowing for equality checks is of questionable value, although we can add it back if need be.

[pksunkara]

I would add it back to maintain as much backward compatibility as possible.

[stuhood]

Copy cannot be added back, since no useful file handles are Copy (without unsafe).

Eq/PartialEq might be possible to add back, but it would need a strange/custom implementation (ie, assigning the Term a unique id?), because neither of those traits is object safe:

error[E0038]: the trait `TermWrite` cannot be made into an object
  --> src/term.rs:28:22
   |
28 |     write: Arc<Mutex<dyn TermWrite>>,
   |                      ^^^^^^^^^^^^^ `TermWrite` cannot be made into an object
   |
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
  --> src/term.rs:15:44
   |
15 | trait TermWrite: Write + Debug + AsRawFd + PartialEq + Send {}
   |       ---------                            ^^^^^^^^^ ...because it uses `Self` as a type parameter
   |       |
   |       this trait cannot be made into an object...

[stuhood]

@pksunkara : Added an optional Style.

Also, the names of structs/methods continue to be completely open to change if you have any thoughts there.

[pksunkara]

I would add it back to maintain as much backward compatibility as possible.