v3.0.0

Added

• Add node 10 to Travis (@ralphtheninja)
• Add browser support to test suite (@vweevers)
• Add airtap for browser tests in Sauce Labs (@vweevers)

Changed

• Update memdown to ^3.0.0 (@vweevers)
• Update encoding-down to ^5.0.0 (@ralphtheninja)
• Update deferred-leveldown to ~4.0.0 (@ralphtheninja)
• Update standard to ^11.0.0 (@ralphtheninja)
• Update level-errors to ~2.0.0 (@ralphtheninja)
• Update bl to ^2.0.0 (@ralphtheninja)
• README: tweak api sub sections (@ralphtheninja)

Fixed

• Fix defunct keyEncoding in inject-encoding-test.js (@vweevers)

Removed

• Remove irrelevant leveldown-substitution-test.js (@ralphtheninja)
• Remove node 4 from Travis (@ralphtheninja)
• Remove batch operations defaulting to put (@vweevers)
• Remove compiler toolchain from Travis (@vweevers)