feat: upgrade to angular 5

[fulls1z3]

** PR Checklist Please check if your PR fulfills the following requirements:

• [x] The commit message follows our guidelines: https://github.com/fulls1z3/ngx-meta/blob/master/CONTRIBUTING.md#commit
• [x] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

** PR Type What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[x] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Other... Please describe:

** What is the current behavior?

Issue Number: N/A

** What is the new behavior?

** Does this PR introduce a breaking change?

[x] Yes
[ ] No

** Other information

[codecov[bot]]

Codecov Report

Merging #127 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #127   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           5      5           
  Lines         177    177           
  Branches       65     65           
=====================================
  Hits          177    177

Impacted Files	Coverage Δ
packages/@ngx-meta/core/src/meta.service.ts	100% <100%> (ø)	:arrow_up:

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