v1.4.0-RC1

Fix

(#275) This allows the PeekPokeTester to us peekAt and pokeAt with SyncReadMem
(#279) Allows working with FixedPoint IOs that are larger than 64 bits
(#288) Interval fixedpoint fixes

Feature

(#236) add fsdb support, fix some typo
(#266) Add a test that shows boring utils works in iotesters
(#274) This allows the PeekPokeTester to us peekAt and pokeAt with SyncReadMem
(#276) Add VSIM backend (Modelsim, Questasim)
(#277) Adjust to the change in global LogLevel from None to Warn.
(#281) Remove trailing comma (breaks 2.11 compilation).
(#282) Bump sbt and tool/plugin dependencies.
(#285) Bump to Scala 2.12.10