Prepare 0.8.1 release

Fix bug #62: Add the hashesPerShareDiff1Divider configuration option to

modify the
Hashrate estimation for algo other than SHA-256 an Scrypt.

0.8.0 release

Allow the value 1 for the workerNumberLimit option.

Prepare next release

Update the API documentation in README

Add an option to remove hash rate history when removing a pool (on the

confirmation window)

Remove an unused dependency

Add missing license headers

Some minor tweaks