Fix treatment of dots at start of line

lib/ronn/roff.rb

@@ -17,7 +17,10 @@ def initialize(html, name, section, tagline, manual=nil, version=nil, date=nil)
     end
 
     def to_s
-      @buf.join.gsub(/[ \t]+$/, '')
+      str = @buf.join
+      str.gsub!(/[ \t]+$/, '')                      # trailing whitespace
+      str.gsub!(/^(\s*)\\\./) { "#{$1}\\[char46]" } # special treatment for lines starting with period
+      str
     end
 
   protected
@@ -269,11 +272,6 @@ def quote(text)
     # write text to output buffer
     def write(text)
       return if text.nil? || text.empty?
-      # lines cannot start with a '.'. insert zero-width character before.
-      if text[0,2] == '\.' &&
-        (@buf.last && @buf.last[-1] == ?\n)
-        @buf << '\&'
-      end
       @buf << text
     end
 

test/dots_at_line_start_test.roff

@@ -7,4 +7,19 @@
 There\'s a weird issue where dots at the beginning of a line generate troff warnings due to escaping\.
 .
 .P
-\&\.\. let\'s see what happens\.
+\[char46]\. let\'s see what happens\.
+.
+.P
+This is also an issue with code blocks
+.
+.IP "" 4
+.
+.nf
+
+\[char46]/example_one
+\[char46]/example_two
+.
+.fi
+.
+.IP "" 0
+

test/dots_at_line_start_test.ronn

@@ -2,3 +2,8 @@ There's a weird issue where dots at the beginning of a line
 generate troff warnings due to escaping.
 
 .. let's see what happens.
+
+This is also an issue with code blocks
+
+    ./example_one
+    ./example_two

test/markdown_syntax.roff

@@ -1447,7 +1447,7 @@ _   underscore
 #   hash mark
 +   plus sign
 \-   minus sign (hyphen)
-\.   dot
+\[char46]   dot
 !   exclamation mark
 .
 .fi