Tweak HOMEBREW_DEVELOPER documentation.

This option does more than just print warnings so let's make a more
generic description with a more specific example.

Closes #716.

Library/Homebrew/manpages/brew.1.md.erb

@@ -145,8 +145,8 @@ can take several different forms:
     of the formula being brewed.
 
   * `HOMEBREW_DEVELOPER`:
-    If set, Homebrew will print warnings that are only relevant to Homebrew
-    developers (active or budding).
+    If set, Homebrew will tweak behaviour to be more relevant for Homebrew
+    developers (active or budding) e.g. turning warnings into errors.
 
   * `HOMEBREW_EDITOR`:
     If set, Homebrew will use this editor when editing a single formula, or

share/doc/homebrew/brew.1.html

@@ -556,8 +556,8 @@ brewed.</p></dd>
 <dt><code>HOMEBREW_DEBUG_PREFIX</code></dt><dd><p>When <code>brew install -d</code> or <code>brew install -i</code> drops into a shell,
 <code>HOMEBREW_DEBUG_PREFIX</code> will be set to the target prefix in the Cellar
 of the formula being brewed.</p></dd>
-<dt><code>HOMEBREW_DEVELOPER</code></dt><dd><p>If set, Homebrew will print warnings that are only relevant to Homebrew
-developers (active or budding).</p></dd>
+<dt><code>HOMEBREW_DEVELOPER</code></dt><dd><p>If set, Homebrew will tweak behaviour to be more relevant for Homebrew
+developers (active or budding) e.g. turning warnings into errors.</p></dd>
 <dt><code>HOMEBREW_EDITOR</code></dt><dd><p>If set, Homebrew will use this editor when editing a single formula, or
 several formulae in the same directory.</p>
 

share/man/man1/brew.1

@@ -767,7 +767,7 @@ When \fBbrew install \-d\fR or \fBbrew install \-i\fR drops into a shell, \fBHOM
 .
 .TP
 \fBHOMEBREW_DEVELOPER\fR
-If set, Homebrew will print warnings that are only relevant to Homebrew developers (active or budding)\.
+If set, Homebrew will tweak behaviour to be more relevant for Homebrew developers (active or budding) e\.g\. turning warnings into errors\.
 .
 .TP
 \fBHOMEBREW_EDITOR\fR