Added navigation bar.
Removed unneeded header file.
Made 404 page neater.
Merge pull request #23 from JGefroh/feature/navigation-bar

FEATURE: Created navigation bar to support more links.
Added link to website.
Made enter key on group input add a task.
Merge pull request #25 from JGefroh/feature/link-to-website

FEATURE: Added a link to my website.
Merge pull request #24 from JGefroh/feature/easy-input

FEATURE: Made pressing Enter on the creation group input field add a task.
Incremented version number to v0.8.0.
Merge branch 'release/v0.8.0'