Lots of 0.7 fixes

Merge pull request #40 from fredrikekre/fe/uninitialized

use uninitialized in OffsetArray constructors

`showarg` and 0.7 inference fix

Merge pull request #32 from JuliaArrays/teh/showarg

Inference improvements on 0.7 and improvements in `show`

Fix array + scalar deprecations

Merge pull request #31 from JuliaArrays/teh/arithdep

Fix ::array + ::Number, for loop, and Val depwarns on 0.7

Fix deprecations

Merge pull request #30 from JuliaArrays/fbot/deps

Fix deprecations