Update pragmas to compile with Solidity v0.6.x + add SPDX comments + bump version

Author: GNSPS

README.md

@@ -8,7 +8,12 @@ The library lets you concatenate, slice and type cast bytes arrays both in memor
 
 Given this library has an all-internal collection of methods it doesn't make sense having it reside in the mainnet. Instead it will only be available in EPM as an installable package.
 
-_Note_: Since version `v0.0.7` the library will only compile on Solidity versions `>0.4.22` so, if you need `v0.4.x` support for your project just use `v0.0.6` of the library with:
+_Version Notes_:
+
+* Version `v0.9.0` now compiles with Solidity compilers `0.5.x` and `0.6.x`.
+
+* Since version `v0.0.7` the library will only compile on Solidity versions `>0.4.22` so, if you need `v0.4.x` support for your project just use `v0.0.6` of the library with:
+
 ```
 $ truffle install [email protected]
 ```

contracts/AssertBytes.sol

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: Unlicense
 /*
  * @title Solidity Bytes Assertion Library
  * @author Gonçalo Sá <[email protected]>
@@ -6,7 +7,7 @@
  *      This library is compliant with the test event convention that the Truffle suite uses.
  */
 
-pragma solidity ^0.5.0;
+pragma solidity >=0.5.0 <0.7.0;
 
 
 library AssertBytes {

contracts/BytesLib.sol

@@ -1,11 +1,12 @@
+// SPDX-License-Identifier: Unlicense
 /*
  * @title Solidity Bytes Arrays Utils
  * @author Gonçalo Sá <[email protected]>
  *
  * @dev Bytes tightly packed arrays utility library for ethereum contracts written in Solidity.
  *      The library lets you concatenate, slice and type cast bytes arrays both in memory and storage.
  */
-pragma solidity ^0.5.0;
+pragma solidity >=0.5.0 <0.7.0;
 
 
 library BytesLib {

contracts/Migrations.sol

@@ -1,4 +1,5 @@
-pragma solidity ^0.5.14;
+// SPDX-License-Identifier: Unlicense
+pragma solidity >=0.5.0 <0.7.0;
 
 
 contract Migrations {

ethpm.json

@@ -1,6 +1,6 @@
 {
   "package_name": "bytes",
-  "version": "0.0.8",
+  "version": "0.0.9",
   "description": "Solidity bytes tightly packed arrays utility library.",
   "authors": [
     "Gonçalo Sá <[email protected]>"