Update dependencies

[LukasKalbertodt]

This is a simple cargo update. The main purpose was to update walkdir
which published a bug fix that affected cargo-sweep in some cases. See
this issue for more information: BurntSushi/walkdir#118

All updates:

      Adding approx v0.1.1
    Updating atty v0.2.11 -> v0.2.13
      Adding autocfg v0.1.5
    Updating backtrace v0.3.9 -> v0.3.33
    Updating backtrace-sys v0.1.24 -> v0.1.31
    Updating bitflags v1.0.4 -> v1.1.0
    Updating cargo-sweep v0.4.0 (/home/lukas/dev/cargo-sweep) -> v0.4.1
    Updating cargo_metadata v0.6.1 -> v0.6.4
    Updating cc v1.0.25 -> v1.0.37
    Updating cfg-if v0.1.6 -> v0.1.9
      Adding cgmath v0.16.1
    Updating clap v2.32.0 -> v2.33.0
    Updating colored v1.6.1 -> v1.8.0
    Updating error-chain v0.12.0 -> v0.12.1
    Updating failure v0.1.3 -> v0.1.5
    Updating failure_derive v0.1.3 -> v0.1.5
    Updating fern v0.5.6 -> v0.5.8
      Adding fuchsia-cprng v0.1.1
    Updating itoa v0.4.3 -> v0.4.4
    Updating lazy_static v1.2.0 -> v1.3.0
    Updating libc v0.2.43 -> v0.2.60
    Updating log v0.4.6 -> v0.4.7
      Adding num-traits v0.1.43
      Adding num-traits v0.2.8
    Updating proc-macro2 v0.4.20 -> v0.4.30
    Updating quote v0.6.9 -> v0.6.13
      Adding rand v0.4.6
      Adding rand_core v0.3.1
      Adding rand_core v0.4.0
      Adding rdrand v0.4.0
    Removing redox_syscall v0.1.40
    Removing redox_termios v0.1.1
      Adding rgb v0.8.13
    Updating rustc-demangle v0.1.9 -> v0.1.15
    Updating ryu v0.2.7 -> v1.0.0
    Updating same-file v1.0.4 -> v1.0.5
    Updating serde v1.0.80 -> v1.0.97
    Updating serde_derive v1.0.80 -> v1.0.97
    Updating serde_json v1.0.33 -> v1.0.40
    Updating strsim v0.7.0 -> v0.8.0
    Updating syn v0.15.18 -> v0.15.39
    Updating synstructure v0.10.1 -> v0.10.2
    Removing termion v1.5.1
    Updating textwrap v0.10.0 -> v0.11.0
      Adding version_check v0.1.5
    Updating walkdir v2.2.6 -> v2.2.9
    Updating winapi v0.3.6 -> v0.3.7
    Updating winapi-util v0.1.1 -> v0.1.2
      Adding winconsole v0.10.0