Buku v2.2

NOTE: Change in dependencies - cryptography, bs4.

Modifications

• Export bookmarks to Firefox bookmarks formatted HTML
• Merge Buku database
• .deb package for Debian and Ubuntu family
• Switch from PyCrypto to cryptography (thanks @asergi)
• Append tags support
• Filter tags for duplicates and sort alphabetically
• Travis CI integration, more test cases (thanks @poikjhn)
• Show DB index in bold in search results
• Several performance optimizations