Add Linux and Windows installation instructions

docs/installation/linux.md

@@ -0,0 +1,39 @@
+Package installation instructions
+=================================
+
+Supports Ubuntu 14.04, CentOS 7.1, and OS X 10.11.
+
+Once the package is installed, `powershell` will be in your path,
+ready to be launched from a terminal. It will read
+`~/.powershell/profile.ps1` for your user profile, and
+`/usr/local/share/powershell/PSL_profile.ps1` for the system profile.
+
+Similarly, it will search `~/.powershell/Modules` and
+`/usr/local/share/powershell/Modules` for user and system modules.
+
+Ubuntu 14.04
+============
+
+Using a stock Ubuntu 14.04 image, download the
+`powershell_0.2.0-1_amd64.deb` file, and then execute the following:
+
+```sh
+sudo apt-get install libunwind8 libicu52
+sudo dpkg -i powershell_0.2.0-1_amd64.deb
+```
+
+CentOS 7.1
+==========
+
+Using a stock CentOS 7.1 image, download the
+`powershell-0.2.0-1.x86_64.rpm` file, and then execute the following:
+
+```sh
+sudo yum install powershell-0.2.0-1.x86_64.rpm
+```
+
+OS X 10.11
+==========
+
+Using an OS X 10.11 machine, download the `powershell-0.2.0.pkg` file,
+double-click it, and follow the prompts.