Update README.md

Added a better description of the project.
Updated the composer file to remove doctrine from the lock file and set the correct version of phpunit
Fixed the database script to be a bit more user friendly, it now prompts the user for deletion and only deletes the database file and not the whole directory
Pa11y test script now can be run from any directory and no longer installs packages if they are missing and instead prints an error to the user.
Fixed database script to use the sqlite3 binary directly as per issue #107
Remove Makefile in favour of Grunt

Available tasks

          sass  Compile Sass to CSS *
     modernizr  Build out a lean, mean Modernizr machine. *
        jshint  Validate files with JSHint. *
        concat  Concatenate files. *
        uglify  Minify files with UglifyJS. *
         clean  Clean files and folders. *
         shell  Run shell commands *
         watch  Run predefined tasks whenever watched files change.
         bower  Manage client-side dependencies via Bower
       compile  Compile JS and Sass files
       install  Run Bower and Composer installs
            js  Concat and minify JavaScript
          test  Run `scripts/test`
          lint  Validate files with JSHint
       default  Does nothing
Update Travis CI config (commands, notifications)
Update README file