implementing more reports
pep8
Merge branch 'master' into reports

Conflicts:
	core/models.py
new layout idea
warn on more browsers
fix #427
show addicional material in lesson page
fix identation
fix activities issues in course page
move course material modal
fix lesson description
fix editing course structure
fix #433 color link of side notes lesson
Merge branch 'master' of github.com:hacklabr/timtec
remove text limitation in lesson description
fix #434
Merge branch 'master' of github.com:hacklabr/timtec
fix #426
now with working backgrounds
fix main-footer and main-nav responsive layout