added clarification for dependencies

Improved clarity of dependencies by adding example of how to install dependencies using apt-get. It was not clear whether `autoreconf -i` would install the dependencies or not. And how to install the dependencies if a user doesn't know how.
made debian apt-get a one-liner
Merge pull request #181 from morenoh149/patch-1

added clarification for dependencies
log: do not show pool difficulty changes on non-current pool.

Keep log spam down when using a lot of vardiff pools, or if a p2pool is
a fallback.
add support for setting algorithm/nfactor for each pool separately, and fix bugged OpenCL thread cleanup (thread shutdown)
Change algorithm more robustly and faster, previous way was buggy
adding mrbrdo to AUTHORS.md for kernel hot-switching