Fix test of `dataframe.rs`
Use `fs::remove_file` to fix error
//! extern crate peroxide;
//! use peroxide::*;
//! use std::error::Error;
+//! use std::fs;
//!
//! fn main() -> Result<(), Box<dyn Error>> {
//! let mut df = DataFrame::with_header(vec!["x", "y", "z"]);
//! df["y"] = vec![0f64; 1000_000];
//! df["z"] = vec![0f64; 1000_000];
//!
-//! // df.write_nc("example_data/df_bench.nc")?;
+//! df.write_nc("example_data/df_bench.nc")?;
//!
//! // read_nc(path: &str, header: Vec<&str>)
//! let dg = DataFrame::read_nc("example_data/df_bench.nc")?;
//! // or read_nc with specific header
-//! // let dg = DataFrame::read_nc_by_header("example_data/df_bench.nc", vec!["x", "z"])?;
+//! let dg = DataFrame::read_nc_by_header("example_data/df_bench.nc", vec!["x", "z"])?;
//! dg.print();
//!
+//! // For test, we remove nc file
+//! fs::remove_file("example_data/df_bench.nc")?;
+//!
//! Ok(())
//! }
//! ```
//! extern crate peroxide;
//! use peroxide::*;
//! use std::error::Error;
+//! use std::fs; // To remove data file
//!
//! fn main() -> Result<(), Box<dyn Error>> {
//! let mut df = DataFrame::with_header(vec!["x", "y", "z"]);
//! let dg = DataFrame::read_csv("example_data/df_bench.csv", ',')?;
//! dg.print();
//!
+//! // For test, remove csv file
+//! fs::remove_file("example_data/df_bench.csv")?;
+//!
//! Ok(())
//! }
//! ```
//! use std::fs::File;
//! use std::error::Error;
//! use std::io::BufWriter;
+//! use std::fs;
//!
//! fn main() -> Result<(), Box<dyn Error>> {
//! let mut df = DataFrame::with_header(vec!["x", "y", "z"]);
//! let json = df.to_json_value();
//!
//! // To write JSON
-//! // let file = File::create("example_data/df_bench.json")?;
-//! // let mut writer = BufWriter::new(file);
-//! // json.write(&mut writer)?;
+//! let file = File::create("example_data/df_bench.json")?;
+//! let mut writer = BufWriter::new(file);
+//! json.write(&mut writer)?;
+//!
+//! // To read JSON (unimplemented)
+//!
+//! // For Test, remove json file
+//! fs::remove_file("example_data/df_bench.json")?;
//!
//! Ok(())
//! }
