added baseURLs method that accepts a sequence of URLs which is more convenient for passing base URLs programmatically.

For example: a list of base URLs passed by a system property outside of
the script.
Patch Request Builder
Remove intToFiniteDurationExpression implicit that messes up with value2Expression
Merge pull request #1337 from israel/master

added baseURLs method that accepts a sequence of URLs which is more conv...
Merge pull request #1338 from sechastain/patch

HTTP Patch Request Builder
Refactor HTTP request builders to be more generic and allow user-defined methods, close #1341
Centralize HTTP warm up code
Make virtualHost an Expression[String], close #1342
Fix previous commit