README typo fix

closes #86
Document and add Argument error for invalidity of using :case_sensitive => false with an expression.

Closes #85
bug fixes: don't dump :case_sensitive => false for index with an expression that includes 'lower(name)', and properly dump multi-column case_insensitive indexes.

Closes #84
attempt to get around rake 10.0.3 issue with ruby 1.9.2 

see https://github.com/jimweirich/rake/issues/157
comment for mysql vs mysql2
When renaming tables, rename constraints

* Was using new table name; fails for > 1 constraint on table
Merge pull request #87 from teleological/v1.0.0-patch

When renaming tables, rename constraints
add spec to test renaming of table with multiple foreign_key constraints.  

see issue #87 and its pull request
bug fix: rename when table has more than one constraint.

it could choosing the wrong index.
fix references matcher to work even if column names aren't specified.  remove redundant file.
add --rspec command and ARGV to runspecs
bug fix: foreign keys should have a consistent default name.

(also, this uncovered that a spec was creating a duplicate constraint.)
update README history
update README history
Accept :length option for index definition

* IndexDefinition member is called :lengths, but dumped/read as :length
* Preserved backwards-compatible support for :lengths
Merge pull request #88 from teleological/v1.0.0-patch-2

Accept :length option for index definition
add spec for index length in migration (mysql only)
Merge branch 'master' of github.com:lomba/schema_plus
no need for backwards-compatibility with incorrect :lengths keyword, since it wasn't working anyway.
README release notes update