[Docs] Only use relative paths

[lfades]

Paths to other documentation files don't need to be absolute, it may cause issues when we start adding versioning to our docs (https://github.com/zeit/next-site/pull/579).

[ijjk]

Stats from current PR

Default Server Mode

General

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
buildDuration	10.2s	10.2s	-44ms
nodeModulesSize	54.5 MB	54.5 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
main-HASH.js gzip	5.05 kB	5.05 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..9ee3.js gzip	12.2 kB	12.2 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	57.2 kB	57.2 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
main-HASH.module.js gzip	4.14 kB	4.14 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	9.2 kB	9.2 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	53.2 kB	53.2 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
polyfills-HASH.js gzip	20.3 kB	20.3 kB	✓
Overall change	20.3 kB	20.3 kB	✓

Client Pages

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_app.js gzip	1.06 kB	1.06 kB	✓
_error.js gzip	2.98 kB	2.98 kB	✓
hooks.js gzip	664 B	664 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	1.9 kB	1.9 kB	✓
routerDirect.js gzip	279 B	279 B	✓
withRouter.js gzip	278 B	278 B	✓
Overall change	7.38 kB	7.38 kB	✓

Client Pages Modern

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_app.module.js gzip	577 B	577 B	✓
_error.module.js gzip	2.08 kB	2.08 kB	✓
hooks.module.js gzip	370 B	370 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	1.48 kB	1.48 kB	✓
routerDirect..dule.js gzip	271 B	271 B	✓
withRouter.m..dule.js gzip	270 B	270 B	✓
Overall change	5.26 kB	5.26 kB	✓

Client Build Manifests

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Rendered Page Sizes

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
index.html gzip	924 B	924 B	✓
link.html gzip	934 B	934 B	✓
withRouter.html gzip	923 B	923 B	✓
Overall change	2.78 kB	2.78 kB	✓

---

Serverless Mode (Decrease detected ✓)

General

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
buildDuration	11.3s	11s	-349ms
nodeModulesSize	54.5 MB	54.5 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
main-HASH.js gzip	5.05 kB	5.05 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..9ee3.js gzip	12.2 kB	12.2 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	57.2 kB	57.2 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
main-HASH.module.js gzip	4.14 kB	4.14 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	9.2 kB	9.2 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	53.2 kB	53.2 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
polyfills-HASH.js gzip	20.3 kB	20.3 kB	✓
Overall change	20.3 kB	20.3 kB	✓

Client Pages

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_app.js gzip	1.06 kB	1.06 kB	✓
_error.js gzip	2.98 kB	2.98 kB	✓
hooks.js gzip	664 B	664 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	1.9 kB	1.9 kB	✓
routerDirect.js gzip	279 B	279 B	✓
withRouter.js gzip	278 B	278 B	✓
Overall change	7.38 kB	7.38 kB	✓

Client Pages Modern

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_app.module.js gzip	577 B	577 B	✓
_error.module.js gzip	2.08 kB	2.08 kB	✓
hooks.module.js gzip	370 B	370 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	1.48 kB	1.48 kB	✓
routerDirect..dule.js gzip	271 B	271 B	✓
withRouter.m..dule.js gzip	270 B	270 B	✓
Overall change	5.26 kB	5.26 kB	✓

Client Build Manifests

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Serverless bundles Overall decrease ✓

	zeit/next.js canary	lfades/next.js remove-absolute-links-to-docs	Change
_error.js gzip	290 kB	289 kB	-684 B
404.html gzip	1.33 kB	1.33 kB	✓
hooks.html gzip	964 B	964 B	✓
index.js gzip	289 kB	289 kB	-299 B
link.js gzip	298 kB	298 kB	-65 B
routerDirect.js gzip	297 kB	296 kB	-1.12 kB
withRouter.js gzip	296 kB	297 kB	⚠️ +724 B
Overall change	1.47 MB	1.47 MB	-1.45 kB

Commit: 6749a59