support cabal sandbox, fixes #62

unfortunately this breaks the support for cabal-dev, so more work is
required.
rename CabalDev.hs to Sandbox.hs

this file is no longer about CabalDev, but about sandboxing support.
describe the two sandbox types

we plan to support both cabal-dev and cabal-sandbox.
find the sandbox path from the sandbox description
uninline cabalSandboxDir
validate package path using a sandbox description
find the package path from the sandbox description

I also had to change a few function names to avoid naming conflicts.
support both cabal-dev and cabal-sandbox
Merge branch 'sandbox-support' into develop
sandbox detection for the test suite, fixes #61

the test suite runs inside ./dist instead of the folder in which hawk is
installed, so we need to make a few educated guesses as to the install
location of the hawk executable.
Merge branch 'test-suite-sandbox' into develop
workaround for resurected ghc bug?

Using the doctest library currently causes the tests to fail with the
following message:

  reference: Too late for parseStaticFlags: call it before newSession

There used to be an issue with that error message in an old version of
ghc [1], not sure why we are triggering it again with a recent version.
Regardless, the workaround is easy: use the executable version of
doctest instead of the library version.

[1] https://github.com/sol/doctest-haskell/issues/11
Revert "workaround for resurected ghc bug?"

This reverts commit 1dd62c4ee1a6c39d34ef4f432837ef665b34b0e0.

I have a better fix coming up.
call doctest first

otherwise, we get the following strange error message:

  reference: Too late for parseStaticFlags: call it before newSession

see the previous two commits for more details.
Merge branch 'doctest-workaround' into develop
change version to 1.0, add gelisam as author and change license to apache2
implement --version, fixes #64
Merge branch 'release-1.0' into develop
detect the version instead of hardcoding it
fix warnings