Support self.extract_value_from_default
It also addresses #394
Merge pull request #395 from yahonda/default_strings_containing_single_quotes

Support self.extract_value_from_default
Remove oracle_enhanced_core_ext.rb
v1.5 supports Rails 4.0 which equires ruby 1.9.3.

Ruby 1.9.3 does not need these `to_d` method fixes.
Merge pull request #397 from yahonda/remove_core_ext

Remove oracle_enhanced_core_ext.rb
Remove unused to_sql_with_foreign_keys and lob_columns
Since #317 merged to master this to_sql_with_foreign_keys method is not used
Merge pull request #398 from yahonda/remove_unused_alias_method_chain

Remove unused to_sql_with_foreign_keys and lob_columns
Remove context indexes after each test
Merge pull request #400 from yahonda/oracle_text_support_12c_sandbox

Remove context indexes after each test
Pending two tests which always fail when tested with Oracle 12c
Needs investigation after some Patch Set Updates and/or Patch Set released
Merge pull request #401 from yahonda/skip_two_tests_when_oracle12c_used

Pending two tests which always fail when tested with Oracle 12c
Use OCI8::Metadata::Base#obj_link to fix rsim/oracle-enhanced#399.
Merge pull request #403 from kubo/issue-399

Use OCI8::Metadata::Base#obj_link to fix rsim/oracle-enhanced#399.
Remove ruby-oci8 v1 code
Merge pull request #405 from yahonda/delete_rubyoci8_v1_code

Remove ruby-oci8 v1 code
Create sequence when add primary_key column
Merge pull request #406 from kassio/master

Create sequence when add primary column
Support Rails 4 Database Tasks
Fixes #402
Merge pull request #404 from avinmathew/rake

Support Rails 4 Database Tasks - Fixes #402
Update History.md for v1.5.2
Merge pull request #411 from yahonda/update_readme_for_v152

Update History.md for v1.5.2