Update documentation for build to fix #76

Author: Jaykul

ReadMe.md

@@ -40,10 +40,18 @@ We have a few modules which are required for building. They're listed in `Requir
 
 #### 3. Run the `build.ps1` script.
 
+By default, the build script uses [gitversion](/gittols/gitversion) to calculate the version of the build automatically:
+
 ```powershell
 .\build.ps1
 ```
 
+If you don't have gitversion handy, you can just specify a version for the `-Semver` parameter:
+
+```powershell
+.\build.ps1 -Semver 2.0.0-beta
+```
+
 #### 4. Make the compiled module available to Powershell
 
 The `.\build.ps1` process will output the path to the folder named with the current version number, like "1.0.0" -- the compiled psm1 and psd1 files are in that folder. In order for PowerShell to find them when you ask it to import, they need to be in the PSModulePath.  PowerShell expects to find modules in a folder with a matching name that sits in one of the folders in your PSModulePath.