Example program to illustrate Stencil basics.

Created a minimal Stencil program that will act as an introduction to
stencil concepts. At this stage it illustrates server side generation,
client-side reconstitution and the use of `pushState` by the client for
subsequent requests.

Closes #39.
Do not build this branch on Travis CI.
Do not constantly reconstitute document.

I was reconstituting the document on each click of forward and back causing the
instance state to become out of sync with the DOM.
Add a module to increment example.

I added a module that will implement the logic of the increment example.
It encapsulates the extraction of the number from the URL path and the
generation of the previous and next link URLs. This illustrates how to
simplify a stencil by pushing the complexity into a module.
Move examples to example directory.

See #126.
Merge the increment example program.

Closes #126.