add Gemfile to project since jekyll gem is invoked by default grunt task

Created by: westonplatter

since we’re using jekyll to compile the github pages, let’s add it as a tool in the listed dependencies so contributors don’t have to guess.

the following is my terminal output before adding the Gemfile

$ grunt

Running "recess:bootstrap" (recess) task File "dist/css/bootstrap.css" created.

Running "recess:min" (recess) task File "dist/css/bootstrap.min.css" created. Original: 125095 bytes. Minified: 102472 bytes.

Running "recess:theme" (recess) task File "dist/css/bootstrap-theme.css" created.

Running "recess:theme_min" (recess) task File "dist/css/bootstrap-theme.min.css" created. Original: 19464 bytes. Minified: 17493 bytes.

Running "jshint:gruntfile" (jshint) task

1 file lint free.

Running "jshint:src" (jshint) task

12 files lint free.

Running "jshint:test" (jshint) task

13 files lint free.

Running "qunit:files" (qunit) task

Testing js/tests/index.html Starting test suite

✔ All tests passed in 'transition' module ✔ All tests passed in 'alert' module ✔ All tests passed in 'button' module ✔ All tests passed in 'carousel' module ✔ All tests passed in 'collapse' module ✔ All tests passed in 'dropdowns' module ✔ All tests passed in 'modal' module ✔ All tests passed in 'scrollspy' module ✔ All tests passed in 'tabs' module ✔ All tests passed in 'tooltip' module ✔ All tests passed in 'popover' module ✔ All tests passed in 'affix' module

Tests completed in 2238 milliseconds 216 tests of 216 passed, 0 failed. OK

216 assertions passed (2238ms)

Running "jekyll:docs" (jekyll) task jekyll build was initiated.

Jekyll output: Warning: Command failed: rbenv: jekyll: command not found

The `jekyll' command exists in these Ruby versions: 2.0.0-p247

Use --force to continue.

Aborted due to warnings.