Remove hard-coded project defaults
Rename mix flag --no-check -> --no-deps-check

Document it and check the flag everytime another task call deps.check.
Do a deps.check after deps.update.
If no deps.check is done use all available deps

Add all available deps to loadpaths even if they didn't pass the deps
check.
Merge pull request #1433 from ericmj/mix-deps-check

Rename mix flag --no-check -> --no-deps-check, document it and use it everywhere