added --enable-tests also to all cabal install commands.
cabal file added for haskell platform 2012.4.0.0
moving PARALLEL_BUILDS option to global for all builds
GHC_VERSION added to the build matrix where HASKELL_PLATFORM is given
commands to prepare the system, such as to install ghc & cabal as per environment variables
command to compile travis build script
new install section of travis YAML for installing dependencies and then raaz packages
new before_script section of travis YAML for configuring and building raaz packages
new script section of travis YAML to run test suites of raaz packages
added a few more sections to travis YAML to make tarball of packages and output final build messages
haskell script to be used to install, build and test raaz packages by travis