Layout feature

[jedireza]

Related to #53 📟 @abritinthebay

• No longer using PLACEHOLDER constant
• Removed the layoutKeyword option
• Fixed bug where HTML doctype wasn't part of the final output
• Layouts must use dangerouslySetInnerHTML={{ __html: this.props.children }} to place the view content
• The same context is passed to both the layout and the view and isn't duplicated/copied
• Copied old examples/layout to examples/layout-component
• Updated examples/layout and examples/remount to use the new layout feature
• Added an event test to examples/remount
• Fixed lab to fail CI if code coverage is below 100%
• Updated dependencies hoek@4, dev dependencies inert@4
• Removed caching options in Travis config

To finish this up:

• [x] Update README with new examples, documentation
• [x] Add tests

[abritinthebay]

oh nice. I like the solution using `dangerouslySetInnerHTML, that's nice and clean. Not sure why I didn't use that originally.

[abritinthebay]

Looks like Vision/Hoek updated and is breaking your tests.

[jedireza]

Besides code coverage failing, locally tests are running are passing. I restarted Travis to see what's up.

[jedireza]

Ok it may have been some caching features added to the Travis config a while ago. I removed those and now we're just failing because of code coverage. 😉

[jedireza]

Once the build passes we should be good to go. @abritinthebay would be willing to give things a final review? Thoughts on the docs?

[abritinthebay]

Docs look good - little sparse but combined with the examples I think it's reasonably clear. Seems solid.