Replace std:: with core:: for bitvec (#123)

.gitignore

 target/
 .DS*
 .*.swp
+.idea
+.vscode
+.DS_Store

src/bit_vec.rs

@@ -14,7 +14,7 @@
 
 //! `BitVec` specific serialization.
 
-use std::mem;
+use core::mem;
 
 use bitvec::{vec::BitVec, bits::Bits, cursor::Cursor, slice::BitSlice, boxed::BitBox};
 use byte_slice_cast::{AsByteSlice, ToByteSlice, FromByteSlice, Error as FromByteSliceError};