Add Docker::Container#copy.

Given a file or directory, will yield each chunk of it.
Version bump 1.5.1 (patch version bump).
Added documentation for Docker::Container#copy.
Made the variable name in Container#copy more clear.

Since Container#copy may output either a file or directory, it was
renamed from file to path.
Added documentation for Docker::Container#delete.
Merge pull request #34 from swipely/add-container-copy

Add container copy
Extracted generic methods from Docker::Image.
Add Docker::Image#insert_local.

Since Docker::Image#insert only accepts a URL, another method was added
to add local files.
Bump the max abc complexity.
Updated Docker::Image#insert_local to be more like Docker::Image#insert.
Patch version bump (1.5.2)
Merge pull request #35 from swipely/add-insert-file

Add insert file
Merge remote-tracking branch 'upstream/master'