Update README.md
Objects's design.
Functionnalize to give another option : -a

-a let download addons accordingly to addons.make file, and that's all!
Correct addon installation. Do a git pull if directory exists.
Correct also bad function ordering.
Update README.md
Update usage message
Fix #33 and #34
Fix #32
Fix #35
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Fix #35
Override PROJECT_CXX et PROJECT_CC to compile on Ubuntu Travis CI