Ignore more Arel calls

Fixes #604

Only run scans when test runs

Handle lambdas in filters instead of blocks

Warn unless a rails 4 app protect[s]_from_forgery with :exception

* Ignore quoted_table_name in SQL (Gabriel Sobrinho)
* Warn about RCE and file access with `open`
* Handle array include? guard conditionals
* Do not ignore targets of `to_s` in SQL
* Add Rake task to exit with error code when fail (masarakki)

Warn about command injection in open()

Cache process_* methods per processor

Ignore quoted_table_name in SQL

Special case `if [...].include? x`

Add rake task to exit with error code when warnings are found

Handle to_s in sql

if the array is all literals and the condition is true, then `x` must
also be one of those literals.

Should fix #638

Don't ignore calls in models outside methods

Ignore primary_key, table_name_prefix, and table_name_suffix in SQL

Fix using --compare and --add-checks-path together