Added short docs to the README (#13)

README.md

@@ -31,6 +31,30 @@
   eval (fnm env --fish)
   ```
 
+## Usage
+
+You can always use `fnm --help` to read the docs:
+
+### `fnm install [VERSION]`
+
+Installs `[VERSION]`. If no version provided, it will install the version specified in the `.nvmrc` file located in the current working directory.
+
+### `fnm use [VERSION]`
+
+Activates `[VERSION]` as the current Node version. If no version provided, it will activate the version specified in the `.nvmrc` file located in the current working directory.
+
+### `fnm ls`
+
+Lists the installed Node versions.
+
+### `fnm ls-remote`
+
+Lists the Node versions available to download remotely.
+
+### `fnm env [--fish]`
+
+Prints the required shell commands in order to configure your shell, Bash compliant by default. Provide `--fish` to output the Fish-compliant version.
+
 ## Future Plans
 - [ ] Add a simpler way of installing it (`curl | bash`?)
 - [ ] Feature: make versions complete the latest: `10` would infer the latest minor and patch versions of node 10. `10.1` would infer the latest patch version of node 10.1