add `trim-whitespace?` setup value (partially resolves #180)

pollen/private/main-base.rkt

@@ -38,7 +38,8 @@
           DOC-ID ; positional arg for doclang-raw: name of export
           (λ (xs)
             (define proc (make-parse-proc PARSER-MODE ROOT-ID))
-            (define doc-elements (splice (strip-leading-newlines xs) (setup:splicing-tag)))
+            (define trimmed-xs (if (setup:trim-whitespace?) (strip-leading-newlines xs) xs))
+            (define doc-elements (splice trimmed-xs (setup:splicing-tag)))
             (proc doc-elements)) ;  positional arg for doclang-raw: post-processor
           (module META-MOD-ID racket/base
             (provide METAS-ID)

pollen/private/ts.rktd

@@ -1 +1 @@
-1534800722
+1535405509

pollen/setup.rkt

@@ -120,7 +120,7 @@
 (define-settable extra-published-path? (λ (path) #f)) ; deprecated in favor of `extra-path?`
 (define-settable extra-path? (λ (path) #f))
 
-
+(define-settable trim-whitespace? #t)
 
 (define-settable here-path-key 'here-path)