fix(collapse): remove element height watching

For unclear reasons the directive was watching DOM element's height
which incurs performance penalty. Normally this watching shouldn't be
necessery as collapsible elements should get height: auto;

Closes #1222
fix(collapse): add the "in" class for expanded panels

Closes #1192
chore(readme): add a note in readme about custom build
docs(README): info on building a subset of modules
refactor(modal): remove unused templates
style(all): rename test files to keep extensions consistent
fix(tooltip): tackle DOM node and event handlers leak

Closes #1133