mkdocs-material-1.0.0-beta.2

Second beta preview release of 1.0.0 which fixes the following issues:

• Fix offset of search when there is no repository information (#70)
• Remove user-scalable=no from viewport meta (#71)
• Add a template block called header for easier overriding (#72)
• Set max-width for images in typesetted content
• Fix height when main content is shorter than sidebar
• Refactored wrapper structure to allow variable-sized sticky footer
• Integrated social icons and moved copyright banner below footer navigation
• Correct horizontal spacing in footer so that it matches header