update dependency list to include libpng and boost 1.55

Xubuntu 14.04 has Boost 1.55 instead of Boost 1.53. Two other tweaks are made to mention that keyboard input is relatively complete and to fix some sample project names.
Merge pull request #2 from pizthewiz/README-dependency-list

Update dependency list with Boost 1.55 and libpng-dev