Fix some doc typos and spacings

Signed-off-by: Kevin Jing Qiu <kevin@idempotent.ca>

docs/understanding-docker.md

@@ -55,7 +55,7 @@ Docker Engine is a client-server application with these major components:
 
 ![Docker Engine Components Flow](article-img/engine-components-flow.png)
 
-The CLI imakes use of the Docker REST API to control or interact with the Docker daemon through scripting or direct CLI commands. Many other Docker applications make use of the underlying API and CLI.
+The CLI makes use of the Docker REST API to control or interact with the Docker daemon through scripting or direct CLI commands. Many other Docker applications make use of the underlying API and CLI.
 
 The daemon creates and manages Docker objects.  Docker objects include images, containers, networks, data volumes, and so forth.
 
@@ -252,7 +252,7 @@ isolated workspace we call the *container*.  When you run a container, Docker
 creates a set of *namespaces* for that container.
 
 This provides a layer of isolation: each aspect of a container runs in its own
-namespace and does not have access outside it.
+namespace and does not have access outside of it.
 
 Some of the namespaces that Docker Engine uses on Linux are:
 

docs/userguide/networking/default_network/container-communication.md

@@ -44,7 +44,7 @@ Many using Docker will want `ip_forward` to be on, to at least make
 communication _possible_ between containers and the wider world. May also be
 needed for inter-container communication if you are in a multiple bridge setup.
 
-Docker will   never make changes to your system `iptables` rules if you set
+Docker will never make changes to your system `iptables` rules if you set
 `--iptables=false` when the daemon starts.  Otherwise the Docker server will
 append forwarding rules to the `DOCKER` filter chain.
 

docs/userguide/networking/dockernetworks.md

@@ -35,7 +35,7 @@ NETWORK ID          NAME                DRIVER
 cf03ee007fb4        host                host
 ```
 
-Historically, these three networks are  part of Docker's implementation. When
+Historically, these three networks are part of Docker's implementation. When
 you run a container you can use the `--net` flag to specify which network you
 want to run a container on. These three networks are still available to you.