add login route

app/templates/common/topnav.html

@@ -18,6 +18,7 @@
     <input type="hidden" name="return_to" value="{{request.path}}">
     <input type="text" placeholder="Username" name="username" autocomplete="username" required>
     <input type="password" placeholder="Password" name="password" autocomplete="current-password" required>
+    <span><input type="checkbox" name="remember" id="remember"> <label for="remember">Remember me</label></span>
     <input type="submit" value="Log in">
     <a href="{{url_for('users.sign_up')}}" class="linkbutton alt">Sign up</a>
   </form>

app/templates/users/log_in.html

@@ -0,0 +1,22 @@
+{% from 'common/macros.html' import subheader %}
+{%- extends 'base.html' -%}
+{%- block title -%}log in{%- endblock -%}
+{%- block content -%}
+{%- set welcome -%}
+Welcome back! No account yet? <a href="{{url_for('users.sign_up')}}">Sign up</a>
+{%- endset -%}
+{{ subheader('Log in', welcome)}}
+{%- if request.args.get('error') -%}
+<div class="infobox plank critical">
+  {{request.args.get('error')}}
+</div>
+{%- endif -%}
+<form class="plank primary-bg full-width" method="POST">
+  <label for="username">Username</label>
+  <input type="text" id="username" name="username" autocomplete="username" required>
+  <label for="password">Password</label>
+  <input type="password" id="password" name="password" autocomplete="current-password" required>
+  <span><input type="checkbox" name="remember" id="remember"> <label for="remember">Remember me</label></span>
+  <input type="submit" value="Log in">
+</form>
+{%- endblock -%}