update for linear

replace R2 with R2 n, suitable constraints on n
fix lerp' to match usage

Follows the argument order in vector-space.
update for linear version of force-layout

More type class constraints in Logo
stylish-haskell
Wall: avoid name shadowing

In liftF & liftF2, `a` and `n` are distinct type variables,
since `f` must operate both on `n ` and `Complex n`
Compatibility with ghc < 7.7.
Clean up type signatures and other small things.
Forgot one.
Add force-layout to travis.
Fix Turtle test.
Add a comment about the `Q236` `Ord` instance
cabal: conservative upper bound on linear
Haddock: function is called `wrapInside`
Merge pull request #40 from diagrams/linear

Migrate from `vector-space` package to `linear`

Make types more polymorphic.