Add snap install instructions

This pull request adds installation instructions for users of [snap enabled Linux distributions](https://snapcraft.io/docs/core/install). Snaps enable ISVs and projects to make their software available to millions of Linux users via the snap store and directly control delivery of software updates to their users.

app/views/docs/installation.html.md

@@ -2,6 +2,14 @@
 
 # Installation
 
+## Linux
+
+Install asciinema in seconds on [Ubuntu and other snap supported Linux distributions](https://snapcraft.io/docs/core/install) with:
+
+    snap install asciinema --classic
+
+Installing a snap is very quick. Snaps contain all necessary dependencies required to run. The snap will get automatically updated when a new version is pushed to the store.
+
 ## Python package
 
 asciinema is available on [PyPI](https://pypi.python.org/pypi/asciinema) and can