Pure javascript function that return the sha1sum

 This package emulate the well know function sha1sum of Node.js in pure
 javascript allowing one to use this function in browser context.
 .
 In cryptography field, SHA-1 (Secure Hash Algorithm 1) is a cryptographic
 hash function designed by the United States National Security Agency
 and is a U.S. Federal Information Processing Standard published by the
 United States NIST, SHA-1 produces a 160-bit (20-byte) hash value
 known as a message digest. A SHA-1 hash value is typically rendered as
 a hexadecimal number, 40 digits long.
 .
 This a dependency of browserify
 .
 Node.js is an event-based server-side JavaScript engine.