Only admins or channels can destroy a project
Calculate contributions' net value taking out fee when appropriate

Method rename to reflect better its meaning.
Remove moip references
Merge pull request #485 from neighborly/im-contribution-net-value

Calculate contributions' net value taking out fee when appropriate
Merge pull request #483 from neighborly/jl-fix-destroy-project-policy

Only admins or channels can destroy a project
Merge pull request #491 from neighborly/jl-remove-moip

Remove moip references
Rename referal_link to referral_url