Update Makefile to also install into /usr/lib

[marcharper]

On Ubuntu variants (and maybe other linux distributions), libstrategies.so is expected to be at /usr/lib/libstrategies.so. Currently after install I have to also run

sudo cp /usr/local/lib/libstrategies.so /usr/lib/libstrategies.so

[marcharper]

Current solution is to export LD_LIBRARY_PATH=$$LD_LIBRARY_PATH:/usr/local/lib