Return 404 instead of 400 when thread not found

Co-authored-by: Greg Price <gprice@edx.org>
Merge pull request #89 from edx/jsa/thread-404

Return 404 instead of 400 when thread not found
Fix active threads endpoint

Previously, pagination was done before reducing from content to threads,
which meant that fewer threads than requested could be returned and that
the number of pages returned could be incorrect.
Merge pull request #96 from edx/gprice/fix-active-threads

Fix active threads endpoint
upgrade tire to 0.5.2, update use of deprecated "text" search api
don't check meaningless "ok" field in output from Tire config endpoint

its value is always true regardless of cluster health, and it is removed
in ES v1.x.
Merge pull request #97 from edx/jsa/tire-match

upgrade tire to 0.5.2, update use of deprecated "text" search api
Remove email from User model and API

It was never actually used for anything except to enforce uniqueness,
which should be done by the LMS.
Merge pull request #99 from edx/gprice/remove-user-email

Remove email from User model and API
Index and query ES using english analyzer
Add rake task to create search indexes
initial import of stream2es wrappers

fixed typo

removed refactor leave behinds

missed push

cr comments

removing extra scheme part

fixed typo, clarified comment
Merge pull request #98 from edx/gprice/english-analyzer

Index and query ES using english analyzer
Merge pull request #100 from edx/e0d/stream2es

E0d/stream2es
minor adjustments to index copying scripts
add migrate-index.sh for simplified reindexing.
Merge pull request #101 from edx/jsa/index-migration

add migrate-index.sh for simplified reindexing.
add create/update dates to comments index, for use in statistical facets
Merge pull request #102 from edx/jsa/index-comments-dates

add create/update dates to comments index, for use in statistical facets
Return total result count for text search queries