Lower coverage threshold to 91.65 percent for mongoid
Optimize images

[ci skip]
Merge pull request #2072 from sferik/squish

Optimize images
Column#primary was removed at Rails4.2
Merge pull request #2073 from tsukasaoishi/for_rails42

Column#primary was removed at Rails4.2
Support Rails 4.2
Remove mongoid-grid_fs version lock
Use String#encode instead of Iconv

Modify to use String#encode instead of Iconv when ASCII Encodings.
There are two reasons:

1. @iconv was defined only encoding_to is NON_ASCII_ENCODINGS
2. Iconv is replaced from ruby-2.0

But when NON_ASCII_ENCODINGS, String#encoding cannot convert then
use Iconv as in the past.
updated routes to rm deprecation warning
Merge pull request #2077 from afxjzs/master

updated routes to rm deprecation warning when running rake test
Support Japanese encodings.
Merge pull request #2078 from mtfuji/master

Support Japanese encodings.
Friendlier error if filter is not found

If user sets, e.g., `filters [:name, :manager]`,
and manager is not set to `filterable true`,
RailsAdmin currently raises a NoMethodError
when trying to call `.type` on nil.

This change raises a more descriptive error
to help the user find the problem
Merge pull request #2079 from nathanl/friendlier_filter_error

Friendlier error if filter is not found
Move navigation out into partial so it can be easily overridden
Merge pull request #2081 from thefrontiergroup/feature/easily_replace_header

Move navigation out into partial so it can be easily overridden
Bump version to 0.6.4
Disallow font-awesome-rails versions >= 5
Disallow sass-rails versions >= 5
Don't package test files with gem