Add support for .fdignore files

[sharkdp]

• Respect .fdignore files
• Do not respect .ignore and .rgignore files (anymore)

See #156

[sharkdp]

There seems to be a small performance regression when using ignore-0.4.1 instead of ignore-0.2.0.

Before:

Benchmark #1: fd -HI '.*[0-9]\.jpg$' '/home/shark'

  Time (mean ± σ):     820.9 ms ±  35.5 ms    [User: 3.654 s, System: 2.547 s]
 
  Range (min … max):   790.1 ms … 904.1 ms

Now:

Benchmark #1: fd -HI '.*[0-9]\.jpg$' '/home/shark'

  Time (mean ± σ):     865.8 ms ±  42.5 ms    [User: 3.994 s, System: 2.454 s]
 
  Range (min … max):   834.5 ms … 975.4 ms

[sharkdp]

Performance regression is due to BurntSushi/ripgrep#835