Improve code CSS style for better readability (#267)

Fix #170.

Author: marcospereira

app/assets/css/modules/_typography.styl

@@ -27,7 +27,7 @@
     h4,
     h5,
     h6 
-        line-height: 1em
+        line-height: 1.3em
         margin-top: 1em
         color: grey-dark
         font-weight: bold
@@ -66,7 +66,7 @@
         font-weight: 300
 
     p 
-        line-height: 1.3em
+        line-height: 1.5em
         margin: 1em 0
 
     p img 
@@ -179,10 +179,9 @@
 
     code 
         height: 4px
-        padding: 0
-        background: #fafafa
+        padding: .2em .4em
+        background: #f2f2f2
         color: #666
-        border: 1px solid #ddd
         border-radius: 3px
         font-family: inconsolata, monospace