Add --max-filesize option to cli

The --max-filesize option allows filtering files which are larger than
the specified limit. This is potentially useful if one is attempting to
search a number of large files without common file-types/suffixes.

See #369.

doc/rg.1

@@ -1,4 +1,4 @@
-.\" Automatically generated by Pandoc 1.19.1
+.\" Automatically generated by Pandoc 1.19.2.1
 .\"
 .TH "rg" "1"
 .hy
@@ -275,11 +275,21 @@ Follow symlinks.
 .RS
 .RE
 .TP
-.B \-m, \-\-max\-count NUM
+.B \-m, \-\-max\-count \f[I]NUM\f[]
 Limit the number of matching lines per file searched to NUM.
 .RS
 .RE
 .TP
+.B \-\-max\-filesize \f[I]NUM\f[]+\f[I]SUFFIX\f[]?
+Ignore files larger than \f[I]NUM\f[] in size.
+Directories will never be ignored.
+.RS
+.PP
+\f[I]SUFFIX\f[] is optional and may be one of K, M or G.
+These correspond to kilobytes, megabytes and gigabytes respectively.
+If omitted the input is treated as bytes.
+.RE
+.TP
 .B \-\-maxdepth \f[I]NUM\f[]
 Descend at most NUM directories below the command line arguments.
 A value of zero searches only the starting\-points themselves.