Cargo Builds.md

Small file change, no dependencies in Cargo.toml:

❯ time cargo build 
        0.06 real         0.04 user         0.02 sys

Fresh build, with Rustbox as the sole dependency:

❯ time cargo build
   Compiling termbox-sys v0.2.9
   Compiling rustc-serialize v0.3.19
   Compiling bitflags v0.2.1
   Compiling winapi-build v0.1.1
   Compiling semver v0.1.20
   Compiling libc v0.1.12
   Compiling num-traits v0.1.35
   Compiling winapi v0.2.8
   Compiling libc v0.2.15
   Compiling kernel32-sys v0.2.2
   Compiling rustc_version v0.1.7
   Compiling rand v0.3.14
   Compiling tempfile v2.1.4
   Compiling num-integer v0.1.32
   Compiling num-iter v0.1.32
   Compiling gag v0.1.9
   Compiling num-bigint v0.1.35
   Compiling num-complex v0.1.35
   Compiling num-rational v0.1.35
   Compiling num v0.1.35
   Compiling rustbox v0.8.1
   Compiling husk v0.1.0 (file:///Users/David/Developer/Rust/husk)
       12.89 real        25.87 user         1.87 sys

Adding a single print!("Hello!"); statement after the previous build:

❯ time cargo build
   Compiling winapi v0.2.8
   Compiling num-traits v0.1.35
   Compiling libc v0.2.15
   Compiling semver v0.1.20
   Compiling bitflags v0.2.1
   Compiling rustc-serialize v0.3.19
   Compiling winapi-build v0.1.1
   Compiling kernel32-sys v0.2.2
   Compiling rustc_version v0.1.7
   Compiling rand v0.3.14
   Compiling tempfile v2.1.4
   Compiling num-integer v0.1.32
   Compiling num-iter v0.1.32
   Compiling gag v0.1.9
   Compiling num-bigint v0.1.35
   Compiling num-complex v0.1.35
   Compiling num-rational v0.1.35
   Compiling num v0.1.35
   Compiling rustbox v0.8.1
   Compiling husk v0.1.0 (file:///Users/David/Developer/Rust/husk)
       12.64 real        22.99 user         1.24 sys