Add test to check package id extraction

This commit add a failing test to check extracting package id. The test will
fail with the following output for now:

1) Cradle.getPackageDbPackages find a config file and extracts packages with their ids
expected: [("template-haskell",Just "template-haskell-2.8.0.0-32d4f24abdbb6bf41272b183b2e23e9c")]
 but got: []

test/data/check-packageid/.cabal-sandbox/i386-osx-ghc-7.6.3-packages.conf.d/template-haskell-2.8.0.0-32d4f24abdbb6bf41272b183b2e23e9c.conf

@@ -0,0 +1,37 @@
+name: template-haskell
+version: 2.8.0.0
+id: template-haskell-2.8.0.0-32d4f24abdbb6bf41272b183b2e23e9c
+license: BSD3
+copyright:
+maintainer: libraries@haskell.org
+stability:
+homepage:
+package-url:
+synopsis:
+description: Facilities for manipulating Haskell source code using Template Haskell.
+category:
+author:
+exposed: True
+exposed-modules: Language.Haskell.TH.Syntax
+                 Language.Haskell.TH.PprLib Language.Haskell.TH.Ppr
+                 Language.Haskell.TH.Lib Language.Haskell.TH.Quote
+                 Language.Haskell.TH
+hidden-modules:
+trusted: False
+import-dirs: /usr/lib64/ghc-7.6.3/template-haskell-2.8.0.0
+library-dirs: /usr/lib64/ghc-7.6.3/template-haskell-2.8.0.0
+hs-libraries: HStemplate-haskell-2.8.0.0
+extra-libraries:
+extra-ghci-libraries:
+include-dirs:
+includes:
+depends: base-4.6.0.1-2bc8d09dc7b7883c4b97d1eb4a9d4ac8
+         containers-0.5.0.0-120bacdd7a06bf9f1f601811aa72d6c3
+         pretty-1.1.1.0-65070790589ca7952412e425f427ac56
+hugs-options:
+cc-options:
+ld-options:
+framework-dirs:
+frameworks:
+haddock-interfaces: /usr/share/doc/ghc-7.6.3/html/libraries/template-haskell-2.8.0.0/template-haskell.haddock
+haddock-html: /usr/share/doc/ghc-7.6.3/html/libraries/template-haskell-2.8.0.0

test/data/check-packageid/cabal.sandbox.config

@@ -0,0 +1,25 @@
+-- This is a Cabal package environment file.
+-- THIS FILE IS AUTO-GENERATED. DO NOT EDIT DIRECTLY.
+-- Please create a 'cabal.config' file in the same directory
+-- if you want to change the default settings for this sandbox.
+
+
+local-repo: /home/me/work/ghc-mod/test/data/.cabal-sandbox/packages
+logs-dir: /home/me/work/ghc-mod/test/data/.cabal-sandbox/logs
+world-file: /home/me/work/ghc-mod/test/data/.cabal-sandbox/world
+user-install: False
+package-db: test/data/check-packageid/.cabal-sandbox/i386-osx-ghc-7.6.3-packages.conf.d
+build-summary: /home/me/work/ghc-mod/test/data/.cabal-sandbox/logs/build.log
+
+install-dirs 
+  prefix: /home/me/work/ghc-mod/test/data/.cabal-sandbox
+  bindir: $prefix/bin
+  libdir: $prefix/lib
+  libsubdir: $arch-$os-$compiler/$pkgid
+  libexecdir: $prefix/libexec
+  datadir: $prefix/share
+  datasubdir: $arch-$os-$compiler/$pkgid
+  docdir: $datadir/doc/$arch-$os-$compiler/$pkgid
+  htmldir: $docdir/html
+  haddockdir: $htmldir
+  sysconfdir: $prefix/etc