Made resources concep tags into a directive

This doesn't change the layout of the tags to match the new design yet
See issue #128 for the designs/plan
Changed layout of resource concept tags to inline

See issue #128
Changed order of tags, requires before teaches

See issue #128
Changed text for resources lacking concepts

e.g., if a resource doesn't require any concepts
Merge pull request #138 from kennib/concept-tags

Concept tags
Rmoved +/- buttons and hid summary text

See issue #129
Added a button to show/hide the summary

See issue #129
Added resource tags to resource summary tile

Style of the tags still needs to be fixed
See issue #129
Made resource summary concept tag labels more visible

See issue #129
Changed style of resource concept tags

See #128 and #129
Fixed resource/concept understanding CSS conflicts
Merge pull request #139 from kennib/resource-summary

Resource summary
Removed knowledge map from the map page

Also removed the resource/concept viewer
See issues #135 and #133
Fixed URLs for resources

See issues #133 #128 #129

URLs for concepts will need to be fixed in #131
Merge pull request #140 from kennib/resource-list

Resource list
Put understanding slider above resource summary

See issue #130
Added a button for reading external resources

See issue #130
Changed +/- button to edit/view button

Removed edit/view tabs
See issue #130
Fixed layout/style of resource page

See issue #130
Fixed undefined concepts bug