Fix TZ data parsing for Julia 0.6

[joshbode]

Julia 0.6 does not provide a function to split a date-time into components.
Parses the string to a DateTime to produce:

[Year, Month, Day, Hour, Minute, Second]

Note: the case of 24:00 is handled prior to parsing to avoid parse failure.

[codecov-io]

Codecov Report

Merging #71 into master will decrease coverage by 0.69%.
The diff coverage is 12.5%.

@@            Coverage Diff            @@
##           master      #71     +/-   ##
=========================================
- Coverage   93.84%   93.15%   -0.7%     
=========================================
  Files          25       25             
  Lines         943      950      +7     
=========================================
  Hits          885      885             
- Misses         58       65      +7

Impacted Files	Coverage Δ
src/tzdata/compile.jl	90.94% <12.5%> (-2.83%)	⬇️

---

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 87155d0...12ec4ec. Read the comment docs.

[joshbode]

Actually, I think this might actually be fixed in v0.6.0-pre.beta where Dates.parse_components appears to have returned.
This was developed using v0.6.0-pre.alpha on which Pkg.build("TimeZones") was failing.