[flow] support for trailing commas

Test Plan: unit test included

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1214228
[flow] support default keyword as method name

Test Plan: now get 100% on graphql-data

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1214231
* lang_js/parsing/ast_js.ml: get rid of Extra
[flow] allow empty jsx body, support more context for jsx

Test Plan:
unit test included
also createflow now parses at 100%

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1214303
[flow] support for variable number of parameters

Test Plan:
unit test included
reach 97% on www

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1214875
[flow] support ":" in xhp attributes

Test Plan:
unit test included
reach 97.5%

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1214964
[flow] fix false positive in regexp using /=

Test Plan: unit test included

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1215098
[flow] support for interpolated strings (aka template strings)

Test Plan:
unit test update
$ ~/pfff/pfff -dump_js backquote.js

[St(
   Variable((),
     [{v_name=("x", ());
       v_init=Some(((),
                    Encaps((),
                      [EncapsString(
                         ("In JavaScript '\n' is a line-feed.", ()))], ())));
       v_type=None; }], Some(())));
 St(
   Variable((),
     [{v_name=("x", ());
       v_init=Some(((),
                    Encaps((),
                      [EncapsString(
                         ("<script>"in quotes without escape"</script>", ()))],
                      ())));
       v_type=None; }], Some(())));
 St(
   Variable((),
     [{v_name=("name", ()); v_init=Some(((), L(String(("Bob", ())))));
       v_type=None; };
      {v_name=("time", ()); v_init=Some(((), L(String(("today", ())))));
       v_type=None; }], Some(())));
 St(
   Variable((),
     [{v_name=("out", ());
       v_init=Some(((),
                    Encaps((),
                      [EncapsString(("Hello ", ()));
                       EncapsExpr((), V(("name", ())), ());
                       EncapsString((", how are you ", ()));
                       EncapsExpr((), V(("time", ())), ());
                       EncapsString(("?", ()))], ())));
       v_type=None; }], Some(())))]

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1215424
* lang_js/parsing/ast_js.ml: cleanup
[flow] support sanitize function in template strings

Summary:

Task ID: #

Reviewers: avik

CC:

Test Plan:
unit test included
reach 98% on www
[flow] support sharp bang

Test Plan: unittest included

Reviewers: avik

Reviewed By: avik

CC: bryano

Differential Revision: https://phabricator.fb.com/D1215642
* changes.txt:
Merge branch 'master' of github.com:facebook/pfff