Top rust-clippy issues

Idea: FIXME lints

C-an-interesting-project E-medium L-lint T-AST

Do not suggest replacing simple `if let Some(_) / None` with methods

C-needs-discussion

Lint suggestions based on MISRA 2004

A-correctness

Suggest more-accurate float functions for hand-written formulas

A-performance E-medium L-lint T-middle good-first-issue hacktoberfest

Suggest `x > y` over `x >= y + 1` for integers

A-style A-unnecessary L-lint T-middle good-first-issue hacktoberfest

Compile error with rustc 1.16.0-nightly (4ecc85beb 2016-12-28)

New lint: missing_panic_doc

L-lint good-first-issue

Better testing of clippy lints before enabling them by default

A-musing C-an-interesting-project

Suggest changing `&mut Vec<_>` parameters to `&mut [_]` when only slice methods are used.

E-medium L-enhancement L-lint

catch `assert!` `assert_eq!` `assert_ne!` and variants in ResultFN

L-lint good-first-issue hacktoberfest