Fix nav issue

Observation: The nav links ul hieght was increased due to addition of new link in it. Due to which the top value of `-600%` couldn't make it hidden in collapsed state.

Fix:
In order make this dynamic, no matter how many links may be added or removed we should have the top value dynamic.

- Observation resulted in conclusion that top should be 100% multiplied by (number of links in nav - 1). So added that as inline style when the nav is in collapsed state.
- Removed top value from styles file. As that is redundant and unnecessary now.

Author: krushiraj

components/common/header/index.js

@@ -92,6 +92,7 @@ class NavBar extends React.Component {
             this.props.router.query.subject.slice(1)} | Coderplex`
         : metaData.title;
     const { description, image } = metaData;
+    const navCollapseStyle = { top: `-${(this.state.navItems.length - 1) * 100}%` };
     return (
       <Headroom>
         <Header>
@@ -109,7 +110,9 @@ class NavBar extends React.Component {
                   />
                 </Link>
               </NavLogo>
-              <NavLinks className={this.state.menuOpen ? 'open' : ''}>
+              <NavLinks
+                className={this.state.menuOpen ? 'open' : ''}
+                style={this.state.menuOpen ? {} : navCollapseStyle}>
                 {this.state.navItems
                   .filter(item => !item.external)
                   .map(item => (

components/common/header/index.styles.js

@@ -48,7 +48,6 @@ export const NavLinks = styled.ul`
     width: 100%;
     position: fixed;
     z-index: -1;
-    top: -600%;
     left: 0;
     background: #fbfbfb;
     border-bottom: 1px solid #eee;