This should make the build faster and more reliable,
and hopefully ressurect the test suite.

Also, add some utilities for working with IHaskell components in `stack
ghci`.

The ihaskell-basic display package has been with us for a while, but
has no useful instances and really doesn't help anyone. We're removing
it for the time being but could get it back someday if needed.

Previously, `cabal install ihaskell` would happily use ipython-kernel-0.8.3, resulting in error

    ‘protocolVersion’ is not a (visible) field of constructor ‘KernelInfoReply’

adjust for changes in Caskroom

ihaskell.cabal: add missing 'here' depend into testsuite

Preprocessing test suite 'hspec' for ihaskell-0.8.4.0...

Hspec.hs:20:18:
    Could not find module ‘Data.String.Here’
    It is a member of the hidden package ‘here-1.2.7@here_1j09jYtlmBB7SYT9WO9k1d’.
    Perhaps you need to add ‘here’ to the build-depends in your .cabal file.
    Use -v to see a list of the files searched for.
Signed-off-by: Sergei Trofimovich <siarheit@google.com>

Fix test example for juicypixels

README: drop lts versions