v0.5.0: Lens + much more docs + better HLint support

• #127:
  Implement Relude.Extra.Lens module.
• #125:
  Moved many numerical functions and types in Relude.Numeric.
  Reexport toIntegralSized from Data.Bits.
  Add integerToBounded and integerToNatural in Relude.Numeric.
• #121:
  Reexport Ap from Data.Monoid. Change definition of foldMapA to use Ap.
• #129:
  Add appliedTo and chainedTo as named versions of operators =<< and <**>.
• #138:
  Add RealFloat to Relude.Numeric.
• #144:
  Add traverseToSnd and friends to Relude.Extra.Tuple.
• #140:
  Improve text of custom compile-time error messages for elem functions.
• #136:
  Cover Relude.Extra.* modules with custom HLint rules.
• #146:
  Improve documentation for Relude.File file: be more explicit about system
  locale issues.
• Improve documentation for One typeclass and add tests.
• Support ghc-8.6.4 and ghc-8.4.4.
  Drop support for ghc-8.6.1 and ghc-8.4.3.