Fix all clippy and rustc warnings (beta toolchain version 0.1.77)

[primeos-work]

The suspicious_open_options lint 0 warns that the truncation behaviour should be made explicit when creating new files. We also set create_new(true), which ensures that a new file will always be created so we should simply drop create(true) since it has no effect anyway: "If .create_new(true) is set, .create() and .truncate() are ignored." 1

The unconditional_recursion lint 2 also emits a warning but that's a false positive and should already be fixed in nightly (see 3 for a very similar case and 4 for the PR that should fix it). In our case we're comparing tuples with just two fields of the Package structure so it isn't recursive.

---

This fixes the following clippy warnings:

[rustup@groot butido]$ cargo clippy --release
   Compiling butido v0.4.0 (/home/rustup/butido)
warning: file opened with `create`, but `truncate` behavior not defined
   --> src/endpoint/scheduler.rs:515:22
    |
515 |                     .create(true)
    |                      ^^^^^^^^^^^^- help: add: `.truncate(true)`
    |
    = help: if you intend to overwrite an existing file entirely, call `.truncate(true)`
    = help: if you instead know that you may want to keep some parts of the old file, call `.truncate(false)`
    = help: alternatively, use `.append(true)` to append to the file instead of overwriting it
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_open_options
    = note: `#[warn(clippy::suspicious_open_options)]` on by default

warning: function cannot return without recursing
   --> src/package/package.rs:224:5
    |
224 | /     fn eq(&self, other: &Package) -> bool {
225 | |         (self.name(), self.version()).eq(&(other.name(), other.version()))
226 | |     }
    | |_____^
    |
note: recursive call site
   --> src/package/package.rs:225:9
    |
225 |         (self.name(), self.version()).eq(&(other.name(), other.version()))
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unconditional_recursion
    = note: `#[warn(clippy::unconditional_recursion)]` on by default

warning: file opened with `create`, but `truncate` behavior not defined
   --> src/source/mod.rs:138:14
    |
138 |             .create(true)
    |              ^^^^^^^^^^^^- help: add: `.truncate(true)`
    |
    = help: if you intend to overwrite an existing file entirely, call `.truncate(true)`
    = help: if you instead know that you may want to keep some parts of the old file, call `.truncate(false)`
    = help: alternatively, use `.append(true)` to append to the file instead of overwriting it
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_open_options

warning: `butido` (bin "butido") generated 3 warnings
    Finished release [optimized] target(s) in 12.57s