* Make the haskell.nix import in the examples explicit
The examples used `import ./. {}` without explaining the commands should
be run from the haskell.nix repo root. To avoid confusion like this I
added fetching a tarball of the repo. This is less efficient when run
from the repo but works when run from anywhere and makes it clear we're
importing haskell.nix.
Added a couple urls and removed the urls on the lens component so as not
to confuse components with packages.
* Fix rephrase
The phrasing was left in a partially-rewritten state.
* Change wording and fix typo
* Minor fixes for consistency
Generalized version of the `cabalProject` and `stackProject`
functions.
Automatically selects the correct project type based on the
`projectFileName` argument if provided or what files exist in
the `src` directory if no `projectFileName` was specified.
If it cannot be determined which it should use the following
error message is given:
```
error: haskell-nix.project : both `stack.yaml` and `cabal.project` files exist set `projectFileName = "stack.yaml;"` or `projectFileName = "cabal.project";`
```
Yvan Sraka
John A. Lotoski
Toon Nolten
Domen Kožar
Hamish Mackenzie