Accept file and http URI in the `-f` flag.

This patch was slightly modified to make it merge correctly against
master
(original patch by @jsvd is #1873)

Closes #1873
Added a task to clean the vendor directory

Fixes #1981
Exposing the rake vendor:clean method to the help message

Fixes #1981
Rake way of deleting files

Fixes #1981
bump kibana to 3.1.2

Fixes #2059
Allow unary operators and comparable on timestamp object closes #2052

Fixes #2061
style preference

Fixes #2061
Some plugin generation fixes.

- Ensure empty lines in some places
- Only print the table if we actually have items to put in there
- Always use inspect function when printing out the defaults

Fixes #2045
Update templates

- Fix empty lines
- Add some more text

Fixes #2045
Modify static docs to work with Generated plugin docs

Fixes #2067
Fix for handling accessor sets on array elements.

Previously: Filters like mutate would throw an exception when attempting
to convert an element within an array to a specific type. This was
raising an error because the index in the field reference was being
treated as a String instead of an integer representing the index of the
field to convert.

Now: Plugins like Mutate can access and convert elements within arrays
to specific types, or, updating their values.