Additional HTTP header support

-H

option to carry an additional HTTP header when performing requests.

Compatible with Elasticsearch 6.x

Add Content-Type: application/json header when requesting.

Preliminary Release #5

Better stdin availability checking when initiated.

Preliminary Release #4

Fix command line option descriptions.

Preliminary Release #4

Fix of command line option parser.

Preliminary Release #3

Changes:

• -r to specify total number of requests, not per thread
• fix calculation bugs

Preliminary Release #2

Changes from the previous release:

• Refactored by C++11 code
• Better thread safe outputs and statistics counters
• -o omit_secs option is replaced with -w wam-up
• $RNUM(max_num) in the URL and the stdin to generate a random number up to max_num
• Default of number of thread and number of recurrence to be 1 sec

Preliminary Release #1

Changes from the previous release:

• Refactored by C++11 code
• Better thread safe outputs and statistics counters
• -o omit_secs option is replaced with -w wam-up
• $RNUM(max_num) in the URL and the stdin to generate a random number up to max_num

Omit the first seconds from the statistics with `-o` option

0.1.4

correct formatting errors