Update tools.md
Update tools.md

Former-commit-id: 3d73b7d99005d3d9145d20f20b2c03255e557794 [formerly 98ee9faa5927bd428a414d608e2956eb2f45cca9]
Former-commit-id: c8bf42175bca4e6ea21daaf714d30d14d11f8cb7
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine