Better header line height (#418)

This change also remote all units for line-height to have more consistent styles and better cascading support. This solve the too small line height for multi line header in article and also add styling for h1 to h6 (previously h3 to h6 was not styled at all)

static/css/_article.scss

@@ -16,7 +16,7 @@ main article {
  	margin: 2.5em auto;
  	font-family: $lora;
  	font-size: 1.2em;
- 	line-height: 1.7em;
+ 	line-height: 1.7;
 
  	a:hover {
  	  text-decoration: underline;
@@ -260,7 +260,7 @@ main .article-meta {
        	padding: 1.25em 0;
        	font-family: $lora;
        	font-size: 1.1em;
-       	line-height: 1.4em;
+       	line-height: 1.4;
        	text-align: left;
       }
     }

static/css/_forms.scss

@@ -34,7 +34,7 @@ textarea {
 
  	font-family: $lora;
  	font-size: 1.1em;
- 	line-height: 1.5em;
+ 	line-height: 1.5;
 }
 
 input[type="checkbox"] {

static/css/_global.scss

@@ -55,13 +55,20 @@ body > main > .h-entry, .h-feed {
 }
 
 main {
+  h1, h2, h3, h4, h5, h6 {
+      font-family: $route159;
+      line-height: 1.15;
+      font-weight: 300;
+
+      &.article {
+          max-width: 40rem;
+      }
+  }
   h1 {
-    font-family: $route159;
     font-size: 2.5em;
-    font-weight: 300;
+    margin-top: 1em;
 
     &.article {
-      max-width: 40rem;
      	margin: 1em auto 0.5em;
      	font-family: $playfair;
      	font-size: 2.5em;
@@ -70,18 +77,27 @@ main {
   }
 
   h2 {
-    font-family: $route159;
    	font-size: 1.75em;
    	font-weight: 300;
 
    	&.article {
-      max-width: 40rem;
       margin: auto;
       font-size: 1.25em;
       margin-bottom: 0.5em;
     }
   }
 
+  h3, h4, h5, h6 {
+      font-size: 1.5em;
+      font-weight: 300;
+
+      &.article {
+          margin: auto;
+          font-size: 1.1em;
+          margin-bottom: 0.5em;
+      }
+  }
+
   .cover {
     padding: 0px;
     margin: 0px;
@@ -175,7 +191,7 @@ p.error {
 
    	font-family: $lora;
    	font-size: 1em;
-   	line-height: 1.25em;
+   	line-height: 1.25;
    	text-align: left;
    	overflow: hidden;
   }