Fix current CI

[AnderEnder]

Looks like windows target on travis is unstable again(could be related to the last rust release).

• Temporary allow windows target to fails.
• Fix clippy flag
• Fix new clippy warnings

[jonhoo]

Would you mind leaving a comment above the added line with a link to this PR?

[codecov-io]

Codecov Report

Merging #123 into master will not change coverage.
The diff coverage is 60%.

@@           Coverage Diff           @@
##           master     #123   +/-   ##
=======================================
  Coverage   89.63%   89.63%           
=======================================
  Files          12       12           
  Lines        1341     1341           
=======================================
  Hits         1202     1202           
  Misses        139      139

Impacted Files	Coverage Δ
src/flamegraph/mod.rs	95.73% <ø> (ø)	⬆️
src/flamegraph/color/mod.rs	75.35% <60%> (ø)	⬆️

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[jonhoo]

What are the other f32 changes for?

[AnderEnder]

New clippy version starts to show new warnings:

warning: casting integer literal to f32 is unnecessary
   --> src/flamegraph/color/mod.rs:290:15
    |
290 |         $b + ($a as f32 * $x) as u8
    |               ^^^^^^^^^ help: try: `50_f32`
...
314 |         BasicPalette::Hot => color!(t!(205, 50, v3), t!(0, 230, v1), t!(0, 55, v2)),
    |                                     --------------- in this macro invocation
    |
    = note: #[warn(clippy::unnecessary_cast)] on by default
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
...