18110a51f2 Bump version of internals to 0.4.0 (Tobin C. Harding)
Pull request description:
In preparation for releasing `internals v0.4.0` bump the version number, add a changelog entry, update the lock files, and depend on the new version in all crates that depend on `internals`.
ACKs for top commit:
apoelstra:
ACK 18110a51f2 successfully ran local tests; lots of nice stuff here
Tree-SHA512: a4d3d5279b7d7fa993cbc3b7b34fc6dc4024dd54c0bfa1ecd0f0d5f09b984871f156c3695092a1f6c44b7571f8b2051699040f5f77636d44d4cae6c972ab597f