Request.multipart no longer crashes when header 'Content-type' is present

Request.multipart used to crash when options contained a header 'Content-type' which is not purely lowercase. That is because hasHeader is case insensitive and returns true and then the split method gets applied to undefined and crashes the application. One could argue that headers should be spelled using only lowercase. However, mixed case headers used to work with a previous version of request, thus I suggest to incorporate this patch to ensure that legacy code does not suddenly crash after updating request.
Merge pull request #715 from pastaclub/master

Request.multipart no longer crashes when header 'Content-type' present
doc: Removed use of gendered pronouns
Merge pull request #719 from oztu/master

Made a comment gender neutral.
README.md: add custom HTTP Headers example.
Merge pull request #724 from tcort/http_headers_example

README.md: add custom HTTP Headers example.
Changing dep.
2.28.0
2.28.1
make request.defaults(options, requester) run the requester for all methods

It wasn't working on PUT and POST before.
Merge pull request #727 from jchris/patch-1

fix requester bug
2.29.0
2.29.1
Fix TypeError when calling request.cookie
Merge pull request #728 from scarletmeow/master

Fix TypeError when calling request.cookie
better DIGEST support
ignore null authValues (DIGEST)
DIGEST support: pass algoritm and opaque, add TODO items, test case for compatible mode
Merge pull request #730 from dai-shi/PR_digest_01

better HTTP DIGEST support
JSHINT: Creating global 'for' variable. Should be 'for (var ...'.