* restored support of multipart/form-data
* paths to the inner packages were changed, because using of absolute paths, like "github.com/gin-gonic/gin/binding", creates some difficulties for contributors,
for example, when I make changes in the "binding" package in tests still used paсkage "binging" from github.com/gin-gonic/gin
* skipped failing tests
* wrote tests for multipart/form-data binding functionality
