Fix for rails 4.1.2

Set default value at type_to_sql
Add columns options at add_column_options!
Use delegate
Merge pull request #8 from SpringMT/master

Fix for rails 4.1.2
bump to 0.1.3
add version badge
fix readme
Add migration case of decimal in migration file
Add unsigned_decimal, signed_decimal spec
Add rails 4.* decimal unsigned migration support
Merge pull request #9 from afunction/master

Support decimal data type in 4.*, and reduce logic complexity
version up 0.2.0
Merge pull request #10 from waka/bump_to_0.2

version up 0.2.0