doc: update BUILDING.md

* General copy-editing

* Move `[sudo] make install` step from general Unix build to own step

* Remove `make test-addons` as that is now covered by `make test`

* Standardize on `/path/to/foo` as used elsewhere in the doc

* Change `node -e` to `./node -e` to avoid using different node binary

PR-URL: #8398
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

BUILDING.md

@@ -1,6 +1,6 @@
 ## Building Node.js
 
-Depending on what platform or features you require the build process may
+Depending on what platform or features you require, the build process may
 differ slightly. After you've successfully built a binary, running the
 test suite to validate that the binary works as intended is a good next step.
 
@@ -25,13 +25,13 @@ On OS X, you will also need:
   * This step will install `gcc` and the related toolchain containing `make`
 
 On FreeBSD and OpenBSD, you may also need:
-* libexecinfo (FreeBSD and OpenBSD only)
+* libexecinfo
 
+To build Node.js:
 
 ```console
 $ ./configure
 $ make
-$ [sudo] make install
 ```
 
 If your Python binary is in a non-standard location or has a
@@ -41,7 +41,6 @@ non-standard name, run the following instead:
 $ export PYTHON=/path/to/python
 $ $PYTHON ./configure
 $ make
-$ [sudo] make install
 ```
 
 To run the tests:
@@ -50,12 +49,6 @@ To run the tests:
 $ make test
 ```
 
-To run the native module tests:
-
-```console
-$ make test-addons
-```
-
 To run the npm test suite:
 
 *note: to run the suite on node v4 or earlier you must first*
@@ -76,11 +69,9 @@ $ make doc
 If you have an existing Node.js you can build just the docs with:
 
 ```console
-$ NODE=node make doc-only
+$ NODE=/path/to/node make doc-only
 ```
 
-(Where `node` is the path to your executable.)
-
 To read the documentation:
 
 ```console
@@ -90,7 +81,13 @@ $ man doc/node.1
 To test if Node.js was built correctly:
 
 ```console
-$ node -e "console.log('Hello from Node.js ' + process.version)"
+$ ./node -e "console.log('Hello from Node.js ' + process.version)"
+```
+
+To install this version of Node.js into a system directory:
+
+```console
+$ [sudo] make install
 ```