Email notifications v1.5 #2

According to @gergely-ujvari, this has already been reviewed by @tilgovi, and he has made modifications to east all his concerns. Thus I am merging this without much further ado.

Merging this. Closes #1066 

This file will be the base for small common services/resources etc. which can be used by any component and not adding any new dependency.
Currently it only has baseurl as a common place to generate the base url which will be used by many components

Changed in two ways:

- Pass irrelevant responses straight through, should they not match
  pattern of {flash, model}
- Handle error responses the same way as regular responses, updating
  the model and flash. This will allow API responses to contain non-2xx
  status responses and still update the model / show flash messages

Yaml assets

Fixed responsiveness on streams, converted search related icons to SVG, eliminated space above topbar

Fixed responsiveness on streams, converted search related icons to SVG, and eliminated space above topbar.

New streamer operators

Angular upgrade v1.2.13

Deleted line that caused the sign in section of the topbar to be abnormally large

In Angular v1.2 what has actually changed about isolate scopes is that
only the directive declaring isolation gets the isolate scope. Its
template will inherit this scope, but other directives on the element
will not. That's the reason ngModel now works with `$parent`.

Everywhere we were binding the controller to the scope it's easier to
use the isolate binding with `=ngModel`.

The isolation scopes are truly isolated better, or evaluation
of the submit handler is happening from the descendent cousin
scopes of the isolated directive. I could probably have moved
the ng-submit handler below the authentication directive, but
I didn't see a compelling reason for the directive to stay in
an isolated scope.

These new operators can match depending the length of a field.
This way we can describe condition like: "filter for replies" because an annotation is reply when len(references) > 0

This moves away from measuring layout of non-typographical elements
in ems, favoring px for better consistency across devices with different
pixel densities. While that may sound backward, the reality is that CSS
pixels are device independent, and non-integer em values seem to be handled
less consistently.

Finally, there were some font size and line height tweaks made here to match
the new measurements of the top bar. This provides a consistent feel to the
top bar across devices and dpi.

Added loading icon suggestion and basic CSS.

Added contributing information and useful resources to the homepage.

Changed icons to give them a consistent style.