Added the dieHolder array -- cleaned up HTML and CSS

#Changes#

##test.js##
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- pushed the **dice** object onto the **dieHolder** array.
- fixed **roll** function in Roll Button test - just changed *roll* to *roll()*.

##main.scss##
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- removed all the default CSS so it's ready for our own stuff.

##app/index.html##
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- removed all the default HTML so it's ready for our own stuff.

##main.js##
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- added the **dieHolder** array.