Split :apropos queries at spaces, treat as conjunction

This makes it easier to narrow queries
:apropos syntax for binders

Together with space splitting, this lets :apropos be used as a kind of
dumber Hoogle. For instance:

```
Idris> :apropos nat -> string
Prelude.Strings.length : String -> Nat
Returns the length of the string.

Idris> :apropos fin -> string

Idris> :apropos fin -> plus

Idris> :apropos fin -> +
Prelude.Fin.+ : Fin n -> Fin m -> Fin (n + m)
Add two Fins, extending the bound

Prelude.Fin.shift : (m : Nat) -> Fin n -> Fin (m + n)
Add some natural number to a Fin, extending the bound accordingly

Prelude.Fin.weakenN : (n : Nat) -> Fin m -> Fin (m + n)
Weaken the bound on a Fin by some amount
```
Document :apropos updates in CHANGELOG
Merge pull request #1189 from david-christiansen/apropos-improvements

Apropos improvements
Run usage analysis after every :r.
Add support for :set warnreach.
Fix Haddock build problems
Merge pull request #1195 from ziman/set-warnreach

Add :set warnreach + usage check after every :r
Merge pull request #1196 from david-christiansen/dos

Fix Haddock build problems
Make Travis build Haddock
Don't compile before building docs in Travis

This makes the build go faster, and Haddock has to type check everything anyway.
javascript: fix elimination of conditions #1192
Merge pull request #1198 from raichoo/javascript

javascript: fix elimination of conditions #1192
Add useful property to Prelude.Vect: xs ++ [] = xs
Merge pull request #1197 from david-christiansen/travisdoc

Make Travis run "make doc" as part of tests
Merge pull request #1199 from david-christiansen/master

Add useful property to Prelude.Vect: xs ++ [] = xs