Create 2018-04-11-launch-handbook.md
Create 2018-04-11-launch-handbook.md

launch the handbook blog post

Former-commit-id: 00485e6ec6b750c7d049f8466e90ae2e554743ce [formerly f3cee5583d147b2fbb66fd284a687b2ec4f49fdb]
Former-commit-id: e4f9e0fffbc9aebad1c7ba47291ee485ae26ecd1
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io