user page modal created, other updates. fixes #95

updated nav bar, moved login/signup to the right side... this needs to be further modified actually. Doesn't look quite right when screen is max size. 

Created user modal, user page shows created dares, attempted dares, contributed dares.  created helper methods for these.

consolidated js files into users.js.

updated dare show such that pot size is updated both in the header and in the label field above the contribution field.