Fix minor type in README.md

Fixes minor typo on line 132.

Before: Designed to inter-operate with your existing JavaScript, `immutable` accepts plain JavaScript [Array] and Objects anywhere a method expects a `Sequence` with no performance penalty.

After: Designed to inter-operate with your existing JavaScript, `immutable` accepts plain JavaScript [Arrays] and Objects anywhere a method expects a `Sequence` with no performance penalty.

This corrects the parallel structure of the clause and slightly improves readability. I'd like to propose additional changes to document grammar and syntax, if desired.
Merge pull request #30 from etripier/Fix-minor-typo-in-README.md

Fix minor typo in README.md
Fix fromEntries return type

Fixes #31.

Previously, grouping a keyed sequence would return each group as an IndexedSequence with nonnumeric keys, which was wrong. This was caused by fromEntries returning an IndexedSequence instead of a keyed sequence. With this, fromEntries always returns a keyed sequence (which matches the type definition) and Sequence's groupBy returns the correct type. (Calling groupBy on an IndexedSequence still gives each group as an IndexedSequence, as before.)

Test Plan: jest
Merge pull request #34 from spicyj/gh-31

Fix fromEntries return type
Adds count() and countBy() as suggested by #27. This provides a much more reasonable API for getting realized lengths solving #33.
add grunt-release
release 2.0.4
add example of using `updateIn` to update a seq, as suggested by #28
Add `update()` as suggested by #24
use smash to assemble a final distribution build, wrapping it in a universal module
Browser getting started
fix universal module
release 2.0.5
better stats
Adds `sort` and `sortBy` as requested by #29
release 2.0.6
Fixed typo.
Merge pull request #48 from rockymadden/master

Fixed typo.
Revert "Fixed typo."
Merge pull request #49 from Lilmoeymoey/revert-48-master

Revert "Fixed typo."