Get config parameter AllCops/Excludes from highest config file in path.

Look upwards towards root for a .rubocop.yml and take Excludes value
from highest file. This solves the problem of .rubocop.yml files in
directories that were supposed to be excluded shadowing the file that
excludes them.

Also fix inherited relative Excludes paths so they are relative to the
.rubocop.yml file that inherits them.
Update CHANGELOG and README.
Merge pull request #295 from jonas054/fix_exclude_problem

Get config parameter AllCops/Excludes from highest config file in path.
Fix Parser dependency to 2.0.0.beta6

Parser 2.0.0 is still beta release.
This means backward compatibility is not always kept,
and RuboCop may break if the dependency version is unfixed.
In development of RuboCop, we need to differentiate
the cause of broken specs. Otherwise we cannot rely on specs.

When a new beta version of Parser is released,
we can check whether RuboCop works properly with the new version
and fix if needed, then update the version of the dependency.

After Parser 2.0.0 official release is done,
we would specify the dependency as range like '~> 2.0'.
Merge pull request #297 from yujinakayama/fix-parser-dependency-version

Fix Parser dependency to 2.0.0.beta6
Let columns start at 1 instead of 0 in all output of column numbers.
Add real_column method to handle the start-from-1 functionality.
Merge pull request #296 from jonas054/fix_column_number

Let columns start at 1 instead of 0 in all output of column numbers.
Add class and module documentation where missing.

Fixed all  Documentation  violations except  unused_local_variable.rb ,
which I think @yujinakayama can do much better.
Merge pull request #298 from jonas054/add_documentation

Add class and module documentation where missing.
Extract variable tracking logic to VariableInspector module
Add class documentation of VariableInspector

This closes #208.
Add specs of VariableInspector and fix NodeScanner.scan_nodes_in_scope
Add new cop ShadowingOuterLocalVariable (#207)
Fix a variable shadowing
Merge pull request #299 from yujinakayama/shadowing-outer-local-variable

Add new cop ShadowingOuterLocalVariable
Fix VariableTable#find_variable_entry behavior if current scope is block

If current scope is block, the method was looking for all outer scope
variables even if the direct outer scope is not block.
Add missing utf-8 encoding comment
New cop WhileUntilDo

The cop tracks uses of `do` in multi-line `while/until` statements.
Break into categories and sort them alphabetically