Fixed Kronecker product of column vectors

Array comprehension returns a 2D array, so I added an explicit 
vectorization after the list comprehension and reordered the 
comprehension indices to get the proper result.
Multiple fixes to kron

Fixed issue 2637, and added support of Kronecker product between 
Vectors and Matrices.
Added tests for Kronecker product

Added simple tests for Kronecker product involving Matrices, 
Vectors and scalars.
Fixed bug in my implementation of Matrix/Vector Kronecker product
base/path.jl: a couple of slight efficiency tweaks.
Add missing transpose solve operators

Quick fix to add missing transpose solve operators with UmfpackLU objects. 

@dmbates
fix download
Simplified Vector/Vector kron and reverted Matrix/Matrix

Simplified Vector/Vector `kron` following 
@andreasnoackjensen's suggestion, and reverted the changes to 
Matrix/Matrix `kron` due efficiency of implementation, as pointed 
out by @JeffBezanson and @andreasnoackjensen.
Added support for Matrix/Vector & Vector/Matrix kron

Both falling back on the Matrix/Matrix case already implemented
size for SymTridiagonal returning incorrect value
Add tests for sparse matrix transpose solve
add mapslices(). closes #2204
this is a beautifully general function. we can use it for #2484
and similar missing functions.
it is also a really good function to focus on optimizing, and for honing
things like indexing behavior.
fix #2661
Changed sleep() to send int64 in start_timer()

On my 32-bit system I was getting 
```ERROR: no method start_timer(TimeoutAsyncWork,Int32,Int32)```
when using ```sleep()```. Changed call to start_timer to use int64s
add Diagonal AbstractMatrix
Merge pull request #2662 from amitmurthy/patch-1

Changed sleep() to call start_timer() with int64s
Merge pull request #2653 from mlubin/patch-1

Add missing sparse LU transpose solve operators
Merge pull request #2660 from KDr2/master

Specify a llvm-config in Make.user when USE_SYSTEM_LLVM=1
Merge pull request #2657 from wlbksy/download

fix #2648
Fix 2663