Note -e/--regexp's additional usefulness.

Specifically, it can be used when searching for patterns that start
with a dash.

Fixes #215

doc/rg.1.md

@@ -35,7 +35,8 @@ the raw speed of grep.
 
 -e, --regexp *PATTERN* ...
 : Use PATTERN to search. This option can be provided multiple times, where all
-  patterns given are searched.
+  patterns given are searched. This is also useful when searching for patterns
+  that start with a dash.
 
 -F, --fixed-strings
 : Treat the pattern as a literal string instead of a regular expression.

src/args.rs

@@ -48,7 +48,8 @@ Common options:
                                [default: auto]
     -e, --regexp PATTERN ...   Use PATTERN to search. This option can be
                                provided multiple times, where all patterns
-                               given are searched.
+                               given are searched. This is also useful when
+                               searching for a pattern that starts with a dash.
     -F, --fixed-strings        Treat the pattern as a literal string instead of
                                a regular expression.
     -g, --glob GLOB ...        Include or exclude files for searching that