Fix first round of review nits

Author: ThadHouse

ni-fpga-sys/Cargo.toml

@@ -7,9 +7,6 @@ license-file = "LICENSE.md"
 description = "Rust bindings to the NI FPGA C API."
 repository = "https://github.com/first-rust-competition/ni-fpga-rs"
 
-build = "build.rs"
-
 [dependencies]
 dlopen = "0.1.8"
 dlopen_derive = "0.1.4"
-libc = "0.2"