Feature/gelf1.1

[nklapste]

Updates graypy to follow the GELF 1.1 standard defined at http://docs.graylog.org/en/3.0/pages/gelf.html.

This will change outputted logs of all handlers! But, should conform to GELF 1.1 much more closely!

Adds better validation to GELF additional fields.

[codecov-io]

Codecov Report

Merging #109 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #109   +/-   ##
=======================================
  Coverage   94.69%   94.69%           
=======================================
  Files           3        3           
  Lines         226      226           
=======================================
  Hits          214      214           
  Misses         12       12

Impacted Files	Coverage Δ
graypy/handler.py	98.75% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 32018c4...5a36d26. Read the comment docs.

[codecov-io]

Codecov Report

Merging #109 into master will increase coverage by 0.1%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #109     +/-   ##
=========================================
+ Coverage   95.97%   96.07%   +0.1%     
=========================================
  Files           3        3             
  Lines         273      280      +7     
=========================================
+ Hits          262      269      +7     
  Misses         11       11

Impacted Files	Coverage Δ
graypy/handler.py	99.53% <100%> (+0.01%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d3d1d85...0b74b7e. Read the comment docs.