Issue #80, add vote_count table to track daily changes in votes.

This table is needed to create the Threshold method. "prev_day_votes" variable will store the
number of votes the idea got the day before, and "curr_day_votes" will store the votes that
the idea will get in the new day. Each time the Threshold method is called, the "curr_day_votes"
column values will be set to 0, and the previous values will overwrite the column "prev_day_votes".
#80, Fix attr_accessible in VoteCount model
Merge pull request #125 from DevYah/C4_Gezeery_#80_dashboard_view_ideas_performance_migrations

Issue #80, add vote_count table to track daily changes in votes. Needed for threshold calculations.