Add dynamic 'back to top' link.
Bold font too distracting.
Merge pull request #104 from yeastgenome/back-to-top-m-3022

Back to top m 3022
Fixed #3009.
Merge branch 'master' into expression-tab
Merge branch 'expression-tab' into v6-lsp

Conflicts:
	src/sgd/frontend/yeastgenome/static/scss/_base.scss
Merge remote-tracking branch 'origin/v6-lsp' into v6-lsp

Conflicts:
	src/sgd/frontend/yeastgenome/static/scss/_base.scss